ClayShannon:

Where is the alt tag supposed to go? Can someone provide an example of one?

OK, I did this, and validator no longer complains about it, so I guess it's alright:

<asp:Image ID="Image1" runat="server" ImageUrl="~/SiteBanner2.PNG" alt="Site Banner" />

<asp:Image ID="Image1" runat="server" ImageUrl="~/SiteBanner2.PNG" alt="Site Banner" />p:Image ID="Image1" runat="server" ImageUrl="~/SiteBanner2.PNG" alt="Site Banner" />

<asp:Image AlternateText="alt text goes here" />

well looks like asp.net defualt genrates a div tag when rendering the girdview control , so do not place inside <p></p> tags rather place the girdview control outside your <p></p> tags ... are you using css adapters with your gridview control ?

 The div is generated by the gridview.

 I would not get so crazy about the WC3 errors. .Net generates html code for a lot of the elements and the WC3 will not like the code generated. Try the site in IE and Firefox and any others you feel will be used to visit your site. If you have only a few minor errors and it displays fine, you don't need to pull your hair out.
 

anthonypj:

well looks like asp.net defualt genrates a div tag when rendering the girdview control , so do not place inside <p></p> tags rather place the girdview control outside your <p></p> tags ... are you using css adapters with your gridview control ?

Great, stripping out the paragraph tags in question solved it. My html now validates as fully compliant.

DarthSwian:

 The div is generated by the gridview.

 I would not get so crazy about the WC3 errors. .Net generates html code for a lot of the elements and the WC3 will not like the code generated. Try the site in IE and Firefox and any others you feel will be used to visit your site. If you have only a few minor errors and it displays fine, you don't need to pull your hair out.
 

That's basically the way I was looking at it, too, but I would much rather have it validate fully (which it now does) than otherwise. You (all) might be interested in this discussion of the web standards issue (the "Martian Headsets" article/blog):

http://www.joelonsoftware.com/