XHTML and CSS validation? Why bother?

Validation is a process that can be used to check a web page for correctness. It is a sound, simple way to ensure that the page is compliant with standards. As XHTML and CSS are formal languages, validating means checking the XHTML and CSS of the page against the formal grammar (called a Document Type Definition or DTD). This post discusses the W3C validators, along with a brief discussion of why they should be used.

The tools to validate Web pages are known as validators. There are validators available for free from the W3C. These validators can check individual pages. There are other validators available (at a cost) that can check an entire site. However, the most up-to-date and definitive validators are from the W3C.

The W3C hosts XHTML and CSS validators that are updated with current standards as they are developed. They can be found at the following locations:

• XHTML validator
• CSS validator

Problems such as unexpected behavior in some browsers or strange layout problems, often occur simply because the XHTML or the CSS contains mistakes. Validating pages to find and remove such errors improves the presentation of the page across user agents.

Validation is…

• the easiest and cheapest method of ensuring quality control for the underlying XHTML and CSS of web pages;
• an efficient way to detect human errors;
• a good net for catching both common and hard-to-spot mistakes, much like a spell check is for content or a compiler is for code; and
• the simplest way you can be sure that your Web pages are indeed complying with the standards.

Validation offers a solid way to investigate problems within a design. Running your pages through a validator allows you to quickly determine the problems by isolating which lines do not comply with the standards. While validators will not catch all problems, they will trap the glaring errors, allowing you to focus your testing efforts on investigating complex or invasive problems instead of merely documenting simple mistakes that are easily fixed.

The proof is in this page

Feel free to use the links at the bottom of this page to test this site’s XHTML and CSS validity. Should you happen to encounter any problems, please let me know.

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