If you running Proxy Server, Mostly it'll store frequently visiting sits content.
It's one of the best feature for fast browsing, But some few cases it not good.
Here a commend for clear cache files from server,
But it not useful at all conditions,
Step 1 : Open terminal and type following
root@localhost~] # echo 3 > /proc/sys/vm/drop_caches
Step 2 : Hit Enter
That's all.
Note : It's not give solution for all problem related with it.