This isn't a problem with the adapters or the kit or its pages.  It's a problem with Visual Studio.

Still, I'm not one who believes in simply saying, "Hey, it's not my problem!"  So, I did a little digging around for you.  It turns out that this problem has been reported already to important people like Scott Guthrie.  See his blog entry from last month.  In particular, take a look at this comment, http://weblogs.asp.net/scottgu/archive/2006/10/20/ASP.NET-AJAX-Beta-1-Released.aspx#706967:

# re: ASP.NET AJAX Beta 1 Released

Sunday, October 22, 2006 4:44 PM by Steve

For: "3. I use nested maserpages. Intellisense doesn't work in VS at all for ASP controls (buttons or anything)." If you are directing that VS bug as being a general bug and not "Atlas" specific, all you need to do is have the nested .master files open in VS, then intellisense works fine....

Basically, the suggestion given here is to open the "content page's" master page if you want to prevent the squiggly lines (which are bogus because they tell you that asp tags are unrecognized when clearly they are correct) and if you want to re-enable intellisense when you type in the "content page."

So, try this experiment...

You said that you already created an instance of the kit's tutorial web site locally.  You calle it CssAdaptersTutorial1.  Open that web site now in VS.  Close all the documents that you happen to have open.  Now open any of the sample pages (e.g., GridView.asp, which lives in the root of the site).  Notice the bogus squiggly lines (which you referred to in your posting above).  Now, while keeping GridView.aspx open in the VS source editor) open its immediate master page, Examples.master.  Click on the tab for GridView.aspx so you can see it in the editor.  Wait second or two... poof, all of the squiggles disappear and intellisense works again!

Cool, huh?