Validating a website is the process of ensuring that the pages on the website conform to the norms or standards defined by various organizations. Validation is important, and will ensure that your web pages are interpreted in the same way (the way you want it) by various machines, such as search engines, as well as users and visitors to your webpage.
Why Validate a Website?
Or, perhaps the better question is what is the meaning of validation?
Simply put, validation of a web page means making the page’s code compliant with the World Wide Web Consortium’s (W3C) standards. This is usually done by checking the HTML & CSS output of your web pages with a validation tool. Just like there are grammar rules in different languages, there are rules in computer programming, too. Validation checks your web page to see if the page follows those rules.
Validation Results in Better SEO
Never forget this fact: Search engine spiders love semantic web pages. It helps those crawlers understand pages better and in SERP listings, you naturally gain advantage against the pages which don’t validate.
Furthermore, it shows that you care about your website. Validating your web page means that you made an effort to have a structural, semantic web page (or you already have the tools or the knowledge to create that page). That’s a huge plus for search engines and that “huge plus” may bump your rankings up.
Validating your HTML and CSS code for standards compliance has certain benefits: it protects your pages from problems arising from syntax errors in your code due to different ways of interpreting errors by the search engines and other browsers. If, however, you have a large number of existing pages that have not been validated and corrected, but nonetheless work well in search engines and other browsers, you might need to consider some sort of strategy (such as the one I used) to prevent webmaster-overload.