Style sheets are loaded asynchonously with documents. This causes the style sheet usually to be applied after at least part of the document has already loaded. Thus the style "pops" into effect. This is distracting. It seems even less sensible that this behavior holds true for cached style sheets. See bug 6541 (which was not reopened for this since it evolved into documenting some other problem). The current "solution" is for document authors to add a proprietary "important" tag to the REL attribute of a LINK element referring to an external stylesheet. This is not an adequate solution, as it requires intervention on the part of the document author. There are millions of legacy documents out on the Web which will not have this tag, and will consequently cause Mozilla to inflict this popping on users.

This is a dup of the now famous bug 17309 "Wait for primary style sheets before constructing frames". *** This bug has been marked as a duplicate of 17309 ***

Marking as verified dup of 17309.