[twitter-bootstrap-3] Bootstrap 3 Glyphicons are not working

If you use Visual Studio (2015, in my case) to create an ASP.NET Webforms Web Application, with Bootstrap theming, by default the glyphicons are stored in the /fonts folder off the project root.

If you start rearranging your bootstrap files under /Content into subfolders (to support multiple themes, for example), all the references within bootstrap to ../fonts/ will break. You can either move the fonts folder to the appropriate relative path under /Content, or else rename all the references from ../fonts to /fonts.