Recently we were using the great EU Cookie Compliance plugin Cookie Control on a client site (also seen on this site bottom left of page), but found that within the custom WordPress Theme that the Cookie Compliance scripts and CSS were loading with a flash of the unformatted and unhidden content. That looked rather ugly so we decided to implement a simple bit of jQuery to hide the Cookie Control Div and content until everythign else (including the script css) was loaded, Here is the jQuery snippet:-
Link this with some very basic CSS:-[css]
/* Cookie Control | Hide until page has loaded */
A second function is commented and that could be uncommented if you had a loading div (such as a spinning wheel etc).
This could also be done with just jQuery like so:-