For important reasons that're too complicated to explain here, several favicons are required for a complex single site.

I am totally new to ASP.NET, but skins are being edited in the ASCX pages. I'd like to put references to these different favicons in the html of skins, but there's no head in the ASCX files.

Where would the code for different favicons belong in the ASCX files?  Thank you for any help.  :)

Favicon is just an ordinary icon with 16x16 pixels images. For best compatibility, there should be an image with 16 colors or 256 colors. Browsers are also able to use the smooth 32bit image with alpha channel. Images with larger sizes are not necessary (unless you want to target users running in high-DPI modes, but the support of that in browsers is very inconsistent) and would only make the icon file larger -> it will take longer to download, so leave them out.

You can create a favicon in any icon editor. Use either RealWorld Icon Editor, or pick up one of the other icon editors (there is a list of icon editors in our directory). If you want to create favicon without installing anything, use an online icon maker. It supports 256 colors with transparency and it can also convert pictures to icons. Once you have the icon, rename it to favicon.ico and upload it on your web server.