Opera recently carried out a report on websites that pass W3C markup validation. The study is part of the Metadata Analysis and Mining Application Project (MAMA) and tested 3,509,170 URLs with the W3C’s markup validator.
The study found that only 4.13% of the URL set passed validation (with 4.33% of the domains having at least 1 URL that passed validation).
While this is a relatively low figure it is an increase on previous years.
In December 2001, 2,034,788 URLs were tested, 14,563 passed, equalling a pass rate of 0.71%
In June 2006, 1,002,350 URLs were tested, 25,890 passed, equalling a pass rate of 2.58%
W3C Validation is arguably not that important, as it does not have an effect on functionality of the website, nor does it affect the rankings in the Search Engine Results Pages.
However it is regarded as important to help ease of maintenance, cross platform compatibility, and access by people with disabilities along with other benefits.
Having a website that is cross browser compatible will help improve traffic and sales conversions as the bounce rate of users viewing a site that appears “broken” will likely be considerably higher than a website that is fully functioning.
Having a website that is accessible to people with disabilities will help improve the number of people able to view your site, which in turn should help increase sales. It is also worth noting that a website that does not take into account people with disabilities is theoretically breaking the law as there is a legal requirement to conform to the disabilities discrimination act. At the moment in time there have been no known cases of these causing webmaster legal issues but as the web becomes more ubiquitous providing access to the disabled will likely become more important.