Here’s what I did:
<link rel="Stylesheet" type="text/css" href="https://stackoverflow.com/questions/34390/Stylesheet.css" id="style" runat="server" visible="false" />
It fools Visual Studio into thinking you’ve added a stylesheet to the page but it doesn’t get rendered.
Here’s an even more concise way to do this with multiple references;
<% if (false) { %>
<link rel="Stylesheet" type="text/css" href="https://stackoverflow.com/questions/34390/Stylesheet.css" />
<script type="text/javascript" src="js/jquery-1.2.6.js" />
<% } %>
As seen in this blog post from Phil Haack.