Thank you for your comments; while I don't agree with all of your points, the fact remains that eCart produces invalid code and the code is inconsistent in this respect. It is not difficult to modify the code but it becomes tedious to do say every time the extension is used, particularly when corrections are overwritten when using the eCart interface to make a minor change. It's often simpler to modify the code directly; with a little work from Webassist, the extension could produce valide code and the interface would be more useful (this applies to other extensions too).
>On the power store page you mention, it actually is not invalid mark-up...<
This illustrates well one of my points - that large numbers of errors make it difficult to spot what may be oversights on the developer's part (rather than shortcomings of the W3 Validator). This page is not valid - there are missing Alt tags, ampersands are not encoded, invalid attributes are used etc..
>This is a known issue that page validators cannot correctly read pages with AJAX and especially Adobe's Spry framework which the page in question does contain three Spry widgets.<
I haven't used Spry much, but I thought these issues had been addressed. However I did use Spry on a site I'm just finishing off, on the Advanced Search feature at the top left of the page on this site:
The page validates; I don't think I had to make any modification to make it do so. I use Ajax on a number of pages and they all validate too (these are in the admin section -I use Ajax to facilitate drag and drop sorting of tables, using a similar method to one you described recently).
Generally I think this is an area Webassist should take more care with. The WA homepage fails validation with a series of extremely basic errors - eg name attributes containing spaces, commas and colons. I don't know if any page is completey valid on the WA site or PowerStore. It doesn't give a very good impression, given the business they're in, and they could easily fix these issues. However I'm more concerned that their extensions should be more professional in this respect.