Your specific quota and overal usage is available in TEACH.
Each user has a soft and hard quota. The soft quota is the amount of disk space that you can use without problems. You can exceed your soft quota for up to one week. If you do not go back below the soft quota within one week, your account will be disabled. You will have to contact support to get your account re-enabled. When you reach the hard quota, you will be unable to write anything more to the disk.
To find out where (what directories) your disk usage is in, type: du -hs *| sort -h. You can also get this information from the quota area of TEACH
Mozilla caches files within your home directory. Often this cache size is too large. If so, you can decrease the cache size within Netscape preferences.