caching

Ok I am dynamically creating images. my problem is my browser is caching the images (or at least half ot them - i see no particular system to which) i have no idea how to stop this. i have tried using the header Cache-Control: no-cahe However it seems to have no helped. maybe i am using it wrongly? is there another method i can clear the browser cache? Thank You, Jon Yaggie www.design-monster.com And they were singing . . . '100 little bugs in the code 100 bugs in the code fix one bug, compile it again 101 little bugs in the code 101 little bugs in the code . . .' And it continued until they reached 0