Image caching

[embert]

YaBB SE Version: 1.5.5
PHP Version: 4.3.4
MySQL Version: 4.0.x
Server Platform: Unix, Linux, or BSD
Link to Forum: http://www.penny-farthing.net/yabbse/index.php

Problem Description:
I have upgraded my forum from YaBB 1.1.3 to YaBB SE 1.5.5 - all went well, but now I notice that the gif images are not being cached - they are reloaded EVERY time a new page loads. This is putting a larger strain on my bandwidth than necessary and leads to increased page loading times.

Is there any way I can get the script to cache the images without caching the text output?

I have a little .htaccess experience, but any changes to this file causes a server 500 error.

Any ideas??

[embert]

Problem solved: my browser's cache was full.