How to make scrollbar transparent which is compatible in all browsers?

Can I make web browsers refresh the cache if it's older than a specified date?

• I've got new navigation images, with the same file names as the old ones. I want to be sure that users pull the new images from the server, rather than showing cached ones. I don't want to completely turn off caching, though, since I've got a lot of rollovers. Is there any way (perhaps an http header) to have browsers refresh cached files only if they're older than a specified date? Thanks!

• Answer:

  I don't believe you can simply force browsers to refresh their cache. You can specify how long something lives in the cache when its first downloaded using the Expires header field, but its too late for you to do that now. The only viable solution is to rename the images, or the entire directory structure if that's simpler.