in your page load event do this:
This keeps your page from being cached. (BTW, if you have files that you don't want other people to steal, dont put them on the web. NOTHING is full proof and if someone wants something bad enough, they will get it eventually. A good example of this is Image sites that used to use the "Disable Right Click" feature and there where how many ways around that! Just some food for thought.)
"The one language all programmers understand is profanity."