We have looked closely at W3C compliance and have moved a long way towards it from v8 onwards.
SellerDeck sites are mostly compliant out-of-the-box but there are two reasons why we aren't compliant in some areas:
- we use our own embedded proprietary tags which enable us to switch between static and dynamic HTML pages. These are non-W3C compliant but the tags are ignored by all browsers
- occasionally we put fixes in to deal with problems in some browsers, i.e. complying would break the display in one or more of the main browsers.
In other words, SellerDeck go as far with compliance as makes sense. It would be possible to fix the first of these points by putting the tags into comments. However, it does not affect SEO rankings and may introduce other problems and afterwards the system will function in exactly the same way.