the best way to avoid cache is to append a dummy parameter in all your
requests sent to the server
like
say you have url http://www.yourdomain.com/page.php?i...eparameter=aaa

then append that url with a dummy parameter which will have a random
value like ....

"http://www.yourdomain.com/page.php?
id=123&someparameter=aaa&dummy=".rand()

this should ask browser to send request to the server and fetch new
response..
but still images and other things in the page would be cached on the
browser side...if u want to avoid that follow the same procedure for
all the request to the server...

--ravi