Internet Explorer 11 and Firefox 38.0.5 cannot open local website running on IIS 7.5

I have the following Sites setup in IIS 7.5

Site---------------Binding----------------------------Path---------
Site1     abc.localhost on *:80 (http)       C:\intepub\wwwroot\abc
Site2     *:323 (http)                       C:\intepub\wwwroot\def
Site3     ghi.localhost on *:80 (http)       C:\intepub\wwwroot\ghi

I have no trouble accessing all three sites using Chrome.

If I use IE 11, I can access Site2 (although the .css is not displaying properly), but I can't access Site1 or Site3 (the error "This page can’t be displayed - Make sure the web address http://abc.localhost is correct." is displayed, and the same error for Site3).

If I use Firefox 38.0.5, I can access Site2 (the .css displays properly), but I can't access Site1 or Site3 (the error "Server not found - Firefox can't find the server at abc.localhost." is displayed, and the same error for Site3). I have made sure that www is not prepended by firefox by setting "browser.fixup.alternate.enabled" to false.

Has anyone experienced this before? It seems that IE and Firefox have trouble accessing sites that have host headers that are not blank. If so, are there settings in IE and Firefox that I have to change so that I can access Site 1 and 3? Thanks.