[TYPO3-english] question about editing in typo3

[tom liu]

I changed some source code in typo3 backend. But after the editing,
the frontend of the  site on my computer is the same(no change) as before.
But when I check it on the other computer, I can see the frontend of the
site has been changed. I am using typo3 4.2.5. How could this happen? Is
this because of cache or cookie? How could I do? I did not see any place in
typo3 backend that I can clear the cache. Please help with this issue.
Thanks.