25 common technical SEO errors and how to fix them

Have you ever wondered why your website gets little traffic even though you invested a lot in content, or why visitors come but do not convert? The cause may well be technical SEO errors you have not noticed. SEO is not only about writing SEO-ready articles. It also means optimizing the whole structure and technical side of the website so Google can crawl it easily and users have a smooth experience. A few small technical errors can noticeably affect your search ranking and traffic.

In this article, let's MONA Media go through common technical SEO errors on websites and how to fix them, so your website runs more smoothly and brings in more customers.

Common onpage SEO errors and how to fix them

When you first start learning SEO, it is hard to avoid some onpage SEO mistakes. Wrong title tags, a missing meta description or badly done content optimization can all make it hard for your site to reach the top. Knowing these errors and how to fix them helps you build a solid foundation and optimize your website effectively and for the long term.

Website speed 

Page load speed is an important SEO factor that Google uses to assess and rank websites. If a site takes more than 3 seconds to load, users lose patience and leave, and they are less likely to buy or use the service. This is one of the most common onpage SEO errors, yet many people overlook it.

Common causes of slow page loading on your website:

• Images not optimized for file size

• Website code that does not meet standards

• Too many unnecessary plugins

• CSS and JavaScript files that are too heavy

How to fix onpage technical SEO errors and optimize the website:

• Check website speed with PageSpeed Insights, GTMetrix or Pingdom

• Optimize images, minify CSS/JS and remove extra plugins

• Upgrade PHP to a newer version (for example PHP 7 for WordPress)

• If needed, hire an expert to optimize speed and set up a staging domain so editing does not affect performance

Mobile user experience not optimized

Today, more than 50% of web traffic comes from mobile devices. Google also ranks websites based on the mobile version first. So failing to optimize SEO for mobile devices is a serious onpage SEO error that directly affects ranking and conversion rate.

Causes of mobile SEO errors:

Technical SEO error: unoptimized URL structure

One of the most common technical SEO errors is a bad URL structure. When URLs are unclear, disorganized or have too many folder levels, both users and search bots struggle to navigate. This also leads to problems such as 404 errors and broken links, which hurt user experience and your Google ranking.

How to check basic technical SEO errors in your website's URL structure:

• Use SEO tools such as SiteBulb, DeepCrawl or Screaming Frog to crawl the whole website.

• Check the Google Search Console reports (Crawl > Errors).

• Test the user experience by searching for a product or service, or by placing a test order, to find navigation errors.

How to quickly fix basic technical SEO errors that affect SEO:

• Plan a clear parent-child URL hierarchy with at most 3 folder levels.

• Keep URLs short, readable and containing related keywords.

• Delete or merge duplicate content, and avoid several pages ranking for the same keyword.

• Check and fix all broken links to keep the experience smooth.

If you are building a website for a business and want to do SEO for the long run, understanding Google's algorithms is a must. In this video Huy goes through the most important algorithms so you start with the right foundation and avoid doing it wrong and having to fix it later.

On-page SEO error: unoptimized meta description

Technical SEO error: unoptimized H1 and Title

The H1 and Title tags are the two most important “storefront” elements of every post. They improve how your site shows up in search engines and draw in readers more effectively. A fairly common on-page SEO error, though, is an H1 or Title that is not set up properly, for example:

• An H1 that is too long (over 70 characters) or a Title over 65 characters.

• No main keyword, or no LSI keywords.

• The H1 and Title are identical.

• A missing H1, or an H1 that is not at the top of the post.

• Many posts on the site share the same Title.

How to spot an unoptimized H1 or Title:

• Use Screaming Frog to check technical SEO errors related to H1 and Title tags.

• Use the search operator allintitle: on Google to see whether your Title duplicates other pages.

How to fix unoptimized H1 and Title tags:

• Place the main keyword and LSI keywords naturally in the H1 and Title.

• Keep the H1 under 70 characters and the Title under 65.

• Make sure the H1 sits at the top of the post and does not repeat the Title.

• Rewrite or replace duplicate Titles so each one is unique and can compete on its own.

Not using internal links to build a link network

Internal linking is one of the most common technical errors that hurt SEO. Internal links pass link strength between pages, help Google understand your site structure, and improve the chance of reaching the top for your keywords. If you don’t use them well, you miss the chance to lift the rankings of several pages at once.

How to spot poorly optimized internal links:

• Check the number and quality of internal links pointing to your important pages.

• Use Google Analytics or Screaming Frog to review inlinks and find pages with too few links.

• Check whether nofollow has been applied to internal links without a good reason.

• See whether anchor text is repeated too often or distributed unnaturally.

How to fix common internal link problems:

• Add related content on other pages and insert internal links pointing to the page you want to rank.

• Use Screaming Frog data to find better opportunities for cross-linking.

• Spread anchor text naturally and avoid keyword stuffing.

• Check and adjust your nofollow rules so they don’t block internal link strength.

A website with too much thin content

Put simply, Google only wants to rank websites with in-depth content that gives users real value. So don’t put too much weight on writing content by SEO strategy but let Google’s own assessment guide you.

A page full of low-quality content hurts SEO. That content does not meet user needs, so conversion rates drop, Google's algorithms and search engines don’t rate the page’s reliability or link structure highly either, which also lowers how often the page gets crawled.

How to spot thin content on your site:

• Crawl the site to find pages with fewer than 500 words.

• Check Google Search Console for notices about content quality.

• Track keyword rankings. If many keywords drop or never reach the top, the content may be too thin.

• Look at bounce rate and time on site: low-quality content usually makes visitors leave quickly.

How to fix this technical SEO error quickly:

• Combine several keywords on the same topic into one in-depth post instead of splitting them across many small ones.

• Add useful content, and bring in video, images, infographics or audio to add value and keep people on the page longer.

• Research what users need before writing, so the content is relevant and engaging.

• Review, update and expand older content regularly so it doesn’t become thin or outdated.

A lot of irrelevant content

Beyond fixing thin content, the content on your site also needs to be coherent, with pages that connect closely to one another. A site with a lot of unrelated content drags down the other sections that are working well. In practice, that shows up as low engagement, or search engines crawling pages that are not SEO,…

To fix a site with too much irrelevant content, keep the following in mind:

• Focus on adding value to your content rather than just hitting the number of posts in the plan.
• For pages you don’t want Google to rank, add them to your robots.txt file.

One of the reasons a website doesn’t reach the top is technical errors that Googlebot notices but we don’t see. Don’t let your site keep making those mistakes. Watch the video to learn how to spot optimization errors on your own site. 

Common offpage SEO technical errors and how to fix them

Besides the on-page technical errors MONA has covered above, avoiding and fixing off-page SEO errors matters just as much.

Here is a summary of the off-page technical SEO errors you should watch closely:

404 errors: one of the most common off-page SEO errors

Technical SEO error: redirects

SEO errors related to the XML sitemap

Sitemap XML plays an important role in technical SEO, helping search engines find their way around and crawl quickly. Many websites, especially large ones with complex structures, make sitemap-related mistakes such as:

• Many pages are not linked to each other, which makes it hard for Google to collect complete information.

• Newly updated content is missed by bots.

• The sitemap includes advanced content that search engines cannot process.

How to fix SEO errors related to the XML sitemap:

• Connect the XML sitemap to Google Search Console so you can monitor it and catch errors early.

• Analyze and check the sitemap regularly to make sure every important URL is indexed.

• If you use a plugin to generate the sitemap, keep it updated and working reliably.

Overusing the canonical tag: a common off-page SEO error

The canonical tag is an HTML element that helps search engines deal with duplicate content. If two pages are nearly identical, you can use a canonical tag to tell search engines which one you want shown. But overusing the canonical tag does more harm than good.

To avoid this mistake, you can try the following:

• Review your pages to check whether any canonical tag points to the wrong page.
• Audit all your content to find other pages with similar content, and see which pages really need a canonical tag.

Misusing robots tags

Robots tags go in the page header, so they can cause a number of problems, especially when they are applied at file level and on individual pages. Several robots tags showing up on the same page is entirely possible. This technical error becomes a barrier that makes the site hard to optimize.

To fix this error, use the following methods:

• When you use Yoast SEO to manage how your robots tags behave.
• Use a plugin that gives you better control over robot behavior.
• Go back and correct the templates where robots tags are placed, following the proper process.
• Add nofollow directives in robots.txt so crawlers don’t waste time searching.

robots.txt errors: another common off-page SEO error

Mistake robots.txt file is a common technical SEO error that directly affects how a website is crawled and indexed. This file tells search engines how to reach your content. If it is misconfigured, important pages can be skipped, which lowers rankings and traffic.

Some common problems:

• Wrong path: The robots.txt file is not in the root directory, or the paths inside the file are incorrect.

• Syntax errors: Syntax mistakes make bots misread or ignore the instructions.

• Blocking important content by mistake: Accidentally blocking folders that hold CSS, JavaScript or key pages.

• File not updated: After the site structure changes or the site is moved, robots.txt is not adjusted in time, which causes crawling and indexing errors.

How to fix robots.txt errors:

• Use Google Search Console to check for robots.txt errors and see which pages are blocked.

• Make sure the file is in the root directory, the syntax is correct, and it does not block important folders or URLs.

• Use Google’s robots.txt tester or a third-party tool to find and fix errors quickly.

• Update the file as soon as the site structure changes so crawling stays smooth.

Unoptimized HTTPS: an off-page SEO error

Google encourages users to move to HTTPS for better security. But quite a few websites overlook this, which hurts their SEO. In particular, the site is less secure and search engines rate it lower.

To optimize HTTPS, you need to get a certificate SSL certificate from a certificate authority if you want to move your site to HTTPS. Once the certificate is installed, your website is better protected.

Unoptimized ALT tags for images

Unoptimized ALT tags (alt text) are a fairly common off-page SEO error. ALT tags help search engines understand what an image shows and act as replacement text when the image does not load. Without proper ALT text, your images struggle to rank on Google Images and are less accessible to users.

How to optimize ALT tags:

• Describe accurately: Write a description that matches the image so both users and search engines understand it.

• Short and to the point: Use brief wording that covers the idea without long explanations.

• Relevant to the page: ALT text should relate to the topic of the post or page that holds the image.

• Avoid keyword stuffing: Use keywords naturally and don’t overdo it.

• Use Vietnamese with diacritics: Keep spelling complete so the text looks professional and reads well for users.

• Check regularly: Review all ALT tags to find and optimize them in time.

Insufficient structured data

Using too little structured data (schema markup), or none at all, is a common off-page SEO error. Schema gives search engines detailed information so they understand your content better and can display it prominently in search results (rich snippets). When schema is missing or incomplete, your website loses its edge in search appearance and SEO performs worse.

How to optimize structured data on your site:

• Check your schema status: Use Google’s structured data testing tool to see whether schema is already in place and whether any data is missing.

• Choose the right schema type: Apply the type that fits your content, such as Article, Product, Event, LocalBusiness, FAQ schemaand so on, to increase relevance.

• Optimize the schema content: Make sure the data is accurate, complete and follows Google’s guidelines so search engines read it correctly.

• Check regularly: Review and update schema whenever your content or site structure changes, to prevent new technical SEO errors.

Homepage with multiple URL versions

A homepage that exists under several URL versions, such as example.com and www.example.com, looks harmless but splits your content, weakens indexing and hurts the homepage’s ranking. It also divides the value of your backlinks, lowers search performance and directly affects overall SEO.

How to fix a homepage with multiple URL versions:

• Check all URL versions of your homepage to see whether they resolve to one standard version.

• Set up 301 redirects from every other version to one canonical URL.

• Set the canonical domain in Google Search Console so search engines recognize the official version.

Other technical SEO errors that hurt website SEO

Technical SEO errors that affect how your site shows up and ranks in search engines include:

Google changes its ranking algorithm

When Google changes its ranking algorithm, it can create SEO problems and lower your keyword rankings, for example:

Causes of technical SEO errors:

Google updates its algorithm often to deliver more accurate and relevant results. With each update, a website’s keyword rankings can jump or drop sharply. It is also how Google patches flaws in older algorithms and adds new criteria.

How to fix the SEO error:

To recover keywords that dropped because of an algorithm change, you can try the following:

• Follow official sources: Keep up with news from Google or reputable SEO sites to understand the goal, scope and recommendations of each update.

• Check your numbers: Use Google Analytics, Google Search Console or other SEO tools to compare traffic and keyword rankings before and after the algorithm change.

• Get expert help: If you lack experience or time, work with a reputable SEO agency to analyze and optimize your site to Google’s new standards.

Low PageRank or poor-quality backlinks

SEO errors tied to PageRank and backlinks usually come from low-quality inbound links from untrustworthy or off-topic websites, for example:

Causes of technical SEO errors:

How to fix this technical SEO error:

To fix low PageRank or poor-quality backlinks, work through these steps with MONA:

• Check your PageRank and backlinks: Use Google Search Console, Google Analytics or SEO tools to analyze the number, quality and source of your backlinks.

• Remove bad backlinks: Contact the site owners to remove the links, or use the Disavow Links tool in Google Search Console to tell Google to ignore them.

• Build quality backlinks: Earn links from relevant, reputable websites with valuable content to improve PageRank and strengthen your rankings.

Website penalized by Google

SEO errors that lead to a Google penalty come from several causes, mostly violations of Google’s content and technical SEO policies.

Causes of technical errors that affect SEO:

Many things can get your website penalized by Google. The most common ones, as MONA has summarized below:

• Using Black Hat SEO: These are SEO techniques that go against Google’s criteria and exploit algorithm loopholes to raise rankings and metrics quickly, but not sustainably.
• Duplicate, low-quality or worthless content: If your site has spam content, copied content, or content unrelated to your topic, Google treats you as a spammer and penalizes you heavily. Google has the Panda algorithm to assess content quality and rank pages accordingly.
• Excessive, low-quality backlink building: Spam links are a technical SEO error that many websites fall into and get penalized for. If you build too many backlinks, spam them from poor sources, or buy and sell backlinks, Google sees it as ranking manipulation and penalizes the site.
• Sabotage by competitors: Sometimes an SEO problem is not your fault at all, but a competitor playing dirty. They may point bad, low-quality backlinks at your site to lower its value in Google’s eyes.
• Other factors: Besides the causes above, other things can get your site penalized, such as too many outbound (external) links, violations of advertising rules, or heavy use of Flash or JavaScript.

How to fix technical website errors that affect SEO:

A Google penalty is something you want to avoid, because it can cut your rankings, traffic and revenue. There are a few ways to check whether your site has been penalized and how to recover:

• Check notices in Google Search Console: This is Google’s free tool for monitoring and managing your website. If your site is penalized, Google Search Console will notify you of the reason and how to fix it. Sign up and use it so you can keep your site under control.
• Check traffic and keyword ranking changes: Another sign of a penalty is a sudden, lasting drop in traffic and keyword rankings. In that case, use tools such as Google Analytics, Google Search Console or SEO software to track changes in traffic and rankings. If you see a big difference after a Google algorithm update, check whether your site violates Google’s webmaster guidelines.
• Check PageRank and index status: PageRank is a Google algorithm that rates the value of a page based on the number and quality of links pointing to it. The index is the set of pages Google has indexed and shows in search results. If your site is penalized, its PageRank and index count will drop, or the site will be removed from Google. You can check both with tools such as Google Toolbar, Google Search Console or SEO software.

Duplicate and outdated content

SEO errors from duplicate and outdated content are a serious problem that can hurt your rankings in search engines. 

Causes of content SEO errors: 

From years of fixing SEO problems for clients, MONA has found that duplicate content and content that isn’t updated regularly are the main reasons keywords slip. Usually the cause is SEOers not keeping close enough watch on the content plan and its execution, so Google rates the site’s quality low.

How to fix content SEO errors: 

The best way to fix poor content is to raise its quality. Look at your competitors’ content, pick out what works and apply it to your own site. Older posts on your site also need to be updated on a regular schedule, so Google rates the site higher.

Poor user experience

A website with a poor user experience will struggle to rank high on Google, because slow loading, hard-to-use layouts and irrelevant content are all negative signals for SEO.

Causes of the SEO error:

A poor user experience is a technical problem that keeps your website from ranking high on Google. Google tends to favor sites that are easy to use on every device, with content that is easy to read and understand and keeps visitors on the page longer.

How to fix the SEO error:

The best fix is to improve the user experience of your website. Here are some things you can try:

• Use white space: White space is the empty area between elements on a page. It creates balance, focus and a clear layout for your content. It makes content easier to read and understand, and it makes calls to action and key information stand out.
• Optimize website speed: To improve speed, use tools such as Google PageSpeed Insights or GTmetrix to analyze current performance and see what needs work. In most cases you will need to optimize images, minify CSS and JavaScript files, or turn on browser caching.
• Use clear calls to action: A call to action (CTA) is a button, link or text that prompts users to take the action you want, such as buying, signing up or contacting you.
• Use a distinct color for links: To help users spot links in your content, use a color that sets them apart from regular text. Blue and green are common choices.
• Break up key information with bullet points: When writing website content, break up the main information with bullet points so readers can picture it and understand it more easily.

Losing rankings to competitors

The rise of competitors is a common reason your SEO keywords drop. When rivals improve their content quality, optimize site performance and build a strong backlink profile, they can overtake you in search rankings and reduce your visibility.

How to fix it and improve your SEO ranking:

To recover, you can take the following steps:

• Analyze competitors’ keywords: You need to know which keywords your competitors use to attract customers and rank high on Google. Tools such as Google Keyword Planner, Spyfu and Keywordspy can show you. You should also pick keywords with high search volume that fit your market and that you can realistically compete for.
• Optimize content for keywords: Once you have chosen your target keywords, create quality, valuable and engaging content for users. Use SEO techniques to optimize that content for the keywords, such as placing them in the title, the opening paragraph, H1, H2 and H3 tags, image alt tags, and internal and external links.
• Build quality backlinks: You can use methods such as guest posting, sharing posts on social networks and forums, joining expert roundups, or creating shareable (viral) content.
• Monitor and evaluate results: Track the results of your SEO strategy to see whether keyword rankings have actually improved. You can use tools such as Google Analytics, Google Search Console or SEO software to follow changes in your site’s traffic and keyword rankings. You should also compare results before and after applying the strategy, and adjust if needed.

SEO errors caused by Google algorithm updates 

SEO errors caused by Google algorithms can cover many different problems, from low-quality content and poor technical SEO to link and user experience issues, for example:

What are SEO errors caused by a Google Penalty?

A Google Penalty is a punishment Google applies when it finds a website breaking its guidelines, usually tied to black-hat SEO or attempts to manipulate search results. Once penalized, a site can lose keyword rankings sharply, see organic traffic drop, or even disappear from search results.

Causes of SEO errors from a Google Penalty:

• Low-quality content: Duplicate or copy-pasted content, keyword stuffing, or auto-generated text.

• Low-quality links: Backlinks from spam or unrelated sites, or bought and sold links used to manipulate PageRank.

• Spam and deceptive practices: Comment spam, forum spam, deceptive redirects and keyword spam.

• Structured data violations: Not following schema markup guidelines, or using wrong or incomplete data.

• Poor hosting or security: A server that hosts many violating sites, malware or spyware, or a full hosting account that slows the site down.

How to fix the SEO error:

• Check whether you have been penalized: Use Google Search Console and Google Analytics to track changes in traffic and keyword rankings.

• Clean up bad backlinks: Remove or disavow low-quality links.

• Upgrade your content: Rewrite posts to SEO standards, update the information, make sure they are more than 95% unique, and give users real value.

• Optimize the website technically: Improve page speed, security and structured data.

• Follow Google’s guidelines: Keep up with algorithm updates, avoid short-term SEO tricks, and build a sustainable strategy instead.

What are SEO errors caused by the Google Panda algorithm?

Google Panda is an algorithm update first released in February 2011, aimed at lowering the rankings of websites with low-quality content and favoring pages with high-quality content. Between 2011 and 2015, Google rolled out about 28 Panda updates to improve search results, remove junk content and push websites to invest in real value for users.

Why a website is hit by Google Panda:

• Thin or low-quality content: Posts that are too short, lack information and give readers no value.

• Duplicate content: Copied from other sites, or repeated across many sub-pages of the same website.

• Lack of trust and authority: Content that doesn’t define its target audience, or has no evidence or reputable sources.

• Content spam: Keyword stuffing, or content stitched together from many sources without editing, which gives a poor user experience.

• Too many ads: Content buried under banners and pop-ups, which hurts the experience and the real value of the page.

How to fix and avoid Google Panda issues:

• Check for and remove duplicate content: Use SEO tools to find, edit or delete repeated content.

• Raise content quality: Write in-depth, complete posts of a sensible length (600 to 2,000 words) in clear, easy language.

• Improve short content: Add useful information, images and video to keep visitors on the page longer.

• Optimizing the user experience: Make navigation logical, limit ads that cover content, and keep pages fast with a layout that is easy to read.

• Build high-quality content: Provide practical information that meets search needs and keeps readers on the page longer.

What are SEO errors caused by the Google Sandbox?

The Google Sandbox is a “control” mechanism Google applies to new websites or new keywords, limiting how well they can rank in search results. Many SEOers compare it to Google’s “probation period.” It usually lasts about 4 weeks, but can run longer if a site is over-optimized or its SEO looks unnatural.

The purpose of the Google Sandbox is to stop new sites, especially those with spam or low-quality content, from “climbing to the top” too fast and hurting the quality of search results.

Why a website ends up in the Google Sandbox:

• A brand-new website with no reputation or track record yet.

• Low-quality or duplicate content, or excessive keyword stuffing.

• A sudden spike in backlinks in a short time, especially low-quality ones.

• Over-doing on-page SEO on a new site (too many anchor texts, multiple H1s, unusually high keyword density).

• Duplicate URLs caused by using the same titles and keywords across many posts.

• Sabotage by competitors, such as hidden links or toxic backlink spam.

How to fix it and shorten the Google Sandbox period:

• Find the cause: Check carefully to identify what triggered the Sandbox, from content and backlinks to site structure.

• Build quality backlinks: Prioritize links from reputable sites in the same field with high traffic. Don’t grow the number of backlinks too quickly.

• Optimize keywords sensibly: Keep keyword density at a safe level (around 1 to 2%), spread it evenly through the post, and mix in secondary keywords and synonyms so the text reads naturally.

• Invest in unique, in-depth content: Write 100% new content that is rich in information and depth, and avoid spun content.

• Control outbound links: Avoid linking out too much, or to low-reputation sites.

• Put White Hat SEO first: Do SEO transparently and focus on value for users rather than quick tricks to “push to the top.”

• Don’t over-optimize a new domain: Go step by step, building content and backlinks slowly to earn Google’s trust.

And don’t miss the latest SEO trend of 2026, where everything gets easier than ever. Watch the video “SEO in 2026 Made Easy in Just 5 Minutes” to pick up the most effective method and climb the rankings fast.

As you can see, there are many mistakes and technical SEO errors that can appear while you carry out an SEO strategy. Even experienced SEOers can’t always avoid them. That is why it is important to stay up to date and fix problems promptly when SEO website they happen. Doing so helps you improve your website and your ranking on Google more effectively. We hope the information on 25+ common technical SEO errors and how to fix them in detail MONA Media shared above is useful to you. Good luck with your fixes.