When developing next theme for Prestashop 1.5, a bug was detected in IE. As it turned out, this browser allows attaching no more than 31 css files using . All that exceeds 31, is just ignored by IE. The bug is present in IE6/7/8/9/10 , i.e. in all versions that are currently available, here is the discussion. Prestashop 1.5 default theme that is crowded with modules, may contain more than 40 css files attached. A way out of the situation for a working e-shop is in using css embedded compression functions.
And when developing a theme, the modules that have already been prepared and that are not to be used in the future, should be disabled.
It also should be noted that such browsers as FF, Opera, Safari and Chrome can easily cope with and manage any number of style files.