This week I got asked if I knew why a Domino-based website lost all its CSS styling when viewed over the internet, whereas it worked fine when viewed via the local intranet.
The browser in question was Internet Explorer and almost instinctively I knew what the cause may be. It's when stylesheets are sent to the browser with the wrong content-type, like with this Page:
Make sure you use "other" and enter "text/css", like so:
Some browsers let you off with this mistake. Some don't (Firefox). IE only allows the wrong content type until viewed with "Internet" settings.
Better safe than sorry and always make sure that the content-type is right!