In early 2009, the web community was asked if they thought there still was a strong motivation for validation. Here are some reasons they mentioned:
Validation as a debugging tool
While most Web browsers do an increasingly good job of parsing even the worst HTML “tag soup”, some errors are not always caught gracefully. Very often, different software on different platforms will not handle errors in a similar fashion, making it extremely difficult to apply style or layout consistently.
Using standard, interoperable markup and stylesheets on the other hand, offers a much greater chance of having one’s page handled consistently across platforms and user-agents. Indeed, most developers creating rich Web applications know that reliable scripting needs the document to be parsed by User-Agents without any unexpected error, and will make sure that their markup and CSS is validated before creating a rich interactive layer.
When surveyed, a large majority of Web professionals will state that validation errors are the first thing they will check whenever they run into a Web styling or scripting bug.
Validation as a future-proof quality check
Checking that a page “displays fine” in several contemporary browsers may be a reasonable insurance that the page will “work” today, but it does not guarantee that it will work tomorrow.
In the past, many authors who relied on the quirks of Netscape 1.1 suddenly found their pages appeared totally blank in Netscape 2.0. Whilst Internet Explorer initially set out to be bug-compatible with Netscape, it too has moved towards standards compliance in later releases.
Validation is one of the simplest ways to check whether a page is built in accordance with Web standards, and provides one of the most reliable guarantees that future Web platforms will handle it as designed.
Validation eases maintenance
It is reasonable to consider that standards such as HTML and CSS are a form of “coding style” which is globally agreed upon. Creating Web pages or applications according to a widely accepted coding style makes them easier to maintain, even if the maintenance and evolution is performed by someone else.
Validation helps teach good practices
Many professionals have been authoring the Web with HTML and CSS for years and know these technologies by heart. Beginners and students, on the other hands, will find automated checking tools invaluable in spotting mistakes. Some teachers also stress that automated validation tests are a good introduction to broader, more complex quality concepts such as accessibility.
Validation is a sign of professionalism
As of today, there is little or no certification for Web professionals, and only a few universities teach Web technologies, leaving most Web-smiths to learn by themselves, with varied success. Seasoned, able professionals will take pride in creating Web content using semantic and well-formed markup, separation of style and content, etc. Validation can then be used as a quick check to determine whether the code is the clean work of a seasoned HTML author, or quickly hacked-together tag soup.
Note: Currently inConcert Web Solutions, Inc. insures W3C validation on all of the websites they release. Furthermore, before release, these new websites are reviewed and tested in Internet Explorer 7 and 8, Firefox, and Google Chrome.
Thank you to http://validator.w3.org for their contribution to this article.