I've seen this in a webcast somewhere, but I can't remember where, and all searching terms I'm trying are coming up unhelpful.
I've got a stylesheet for my site, and it's referenced in a master page. Child pages that use this master page use these styles, but .Net doesn't know about them. When the site is run, it all works great, but I'm trying to figure out how to get .Net to know about them at design time.
This should also fix the issue with not knowing about the javascript files I'm including, too -- I think it's all related and I can't for the life of me figure out how.
EDIT: I'm an idiot. This is the code that was being used to include the stylesheet.
<link href="<%= ResolveUrl("~/") %>css/styles.css" rel="stylesheet" type="text/css" />
I hate people who overthink things. Oh, and people who are too stupid to fully investigate an issue before they ask a question. Like me.