I recently ran across a website for a local website development company and in the process of checking out their services and portfolio I noticed something peculiar: All the sites they developed use 100% valid HTML code. As an SEO, I appreciate a developer that cares enough about their end product that they take the time to produce quality code along with quality designs.

But what does valid code have to do with SEO? Honestly, not a whole lot. HTML validation is completely unnecessary to the optimization process. The only thing the SEO needs to be sure of is that there are no problems in the code structure that would prevent the search engine spider from parsing the code correctly.

Most browsers are very forgiving of bad code. If the browser can interpret the intention (for lack of a better word) of the programmer then it will likely display the page as intended. But search engine spiders are often not as forgiving and simply not closing a tag can cause the spider to read the code structure completely different from how the page is displayed in the browser.

While a page may still get ranked for keywords, the poorly developed code may actually be prohibiting the page from performing as well as it otherwise could.

The solution here is to validate your code if possible. While its only important to find any offending code errors that may be "spider stoppers", validating your code 100% will not only find all such offenses, but it will make it easier to find them in the future.

Let's say you find and fix all your spider stopping code errors but don't go on to validate the rest of your code. That's reasonable. That validation can take a good amount of time and ultimately not provide any end benefit. The spider stopper is gone, that's all that needs to be done. But inevitably your website will be edited and on occasion, some additional bad code may be added back in, potentially even spider stopping code.

Most likely you'll go on and never realize this happened even after (if) search engine rankings begin to decrease. Persistent 100% validation of your website pages ensures that you find any and all new spider stopping errors as soon as they happen. Not having valid code makes it much more difficult to find newly added bad code that can effect the search engine spiders. Keeping code validated ensures that you find any potential problems each time you update your site and check for validation errors.

In the grand scheme, I believe that code validation is not necessary, but important. At the very least its a way to quickly and easily spot potential coding problems.