Dreamweaver lets you call your files any name that works on your operating system, even something like "don't forget this is the photo the boss likes," but be aware that your Web server may use a different operating system that's more restrictive. Many of the servers on the Web are run on UNIX machines, which are not only case-sensitive, but they also don't allow spaces or special characters, except for the underscore ( _ ). So coming up with names that work and that you — and everyone else on your site development team — can remember can be difficult.