E-mail:
An abuser can read your incoming and outgoing mail. Change your password often. Get creative with the password. You want to make it hard for them to discover it. Hide it in a safe place.
History and Cache File:
Clear these everytime you are on finishing with the computer. The abuser can read the (automatically saved web pages and graphics), and discover your acitivity.
You can clear your history and empty your cache files in your browser's settings.
Netscape:
Pulldown Edit menu, select Preferences. Click on Navigator on choose Clear History. Click on Advanced then select Cache. Click on Clear Disk Cache.
Please be careful and use all these steps above that apply to your browser of choice.