That is good, you may also want to consider checking IE 7 with the IE web developer toolbar as well. I know that I have run into differences with how the two handle things. I also like the IE web developer toolbar for its click on an element and it gives you all of its attributes a little easier to follow that the firefox toolbar.
Somtimes tables are unavoidable with dnn it seems because the solpartmenu runs on tables....(very 90's web of it) but take a look at athletics.cazenovia.edu that is the closest ive come to table free and compliant to w3c. I assure you that when I developed the html and the css for the skin before uploading the package to dnn it was w3c compliant. I have been reading that the webconfig file needs to be changed to meet xhtml compliance but I am leary of changing things in the webconfig because of other modules dependancy on it.
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