Due to network or some other reasons, some sites do not have their css files loaded and you will see unformatted/un-layout-ed ugly page.
It happened to pages I did before also. Kind of beyond control from a developer/design point of view.
I'm thinking of something like this place at the top of the page and obvious:
/*.... header and stuff */
<body>
<h2 id="hiddennote">If you do not see this page properly, please refresh</h2>
/*.... rest of the page .... */
The external stylesheet have a definition like this:
/* other styles defined */
#hiddennote {display: none;}
Functionally I know it'll work. Any drawbacks?