ASP.NET page is not loading CSS styles

Question

This is a simple website in ASP.NET with C# using VS 2010. I have following directory structure for this project:

Answer 1

The stylesheets included in your master page are using relative paths.

Specify your stylesheet links with runat=server and prefix them with the virtual web root path (~):

OR:

But keep in mind that the first option is recommended. The second will not work when you publish your site in a virtual directory.

After last comment...

The image URL's in CSSs should be updated as well, in order to not use relative paths or do any path traversal (../).

background: #fff url(images/img01.jpg) repeat-x left top;

For this option you will need to move the images folder inside the Styles folder (it's a good practice to do so).

Final update:

Looks like that the head element also needs to be runat=server in order for ASP.NET relative paths (~) to work within link elements with runat=server.