Problem with memory

HI

I have a box running RH 9.0 running as a local web server, the problem is when i first run it and type :
# free -m it shows that 44MBB are used
after a while without doing something
free -m shows this time 215MB

what's the problem if this sudden rise of memory usage ?
i check my services all seems normal , there's no scheculed tasks no Cron runnig and no one is connected to the server. i isolated from my lan but the problem remain !! is it a problem ?
my config is:
P4 2.5GHZ
256 MB RAM
40 GB hd
RH 9.0
Apache 2.0.52

thanks for all

Don't worry, this is typical behaviour of linux. It just uses free memory for caching and other things, but memory will be released if it is needed