Why is /var so big?

[Rob Rosenthal]

Okay, yum is broken. Here's the error message:

Unable to find pid
Gathering header information file(s) from server(s)
Server: Fedora Core 2 - i386 - Base
Traceback (most recent call last):
 File "/usr/bin/yum", line 30, in ?
   yummain.main(sys.argv[1:])
 File "/usr/share/yum/yummain.py", line 233, in main
   clientStuff.get_package_info_from_servers(serverlist, HeaderInfo)
 File "/usr/share/yum/clientStuff.py", line 838, in 
get_package_info_from_servers
   os.mkdir(servercache)
OSError: [Errno 2] No such file or directory: '/var/cache/yum/base'

Now how do I fix it?