The only time I've ever experienced CSS changes not being immediately applied is when the change was made to an external sheet that was being applied via an @import statement in the linked external CSS file.
Meaning in the xhtml:
Code:
<link href="../Styles/MainStyle.css" type="text/css" rel="stylesheet"/>
in MainStyle.css:
Code:
@import url(../Styles/epub.css);
and finally in epub.css:
Code:
p.blah { text-indent:1.2em; }
Changes to epub.css would not take effect until a Sigil restart.