Safe Web Browsing
Apart from email risks, surfing the net or browsing is probably the biggest security risk as far as online security goes.
Microsoft's Internet Explorer is so riddled with vulnerabilities that to just not use it at all, is probably the single most easy step you can take.
This is not to knock Microsoft too much, it's just that IE is by far the most popular browser, therefore the 'Bad Guys' target it more frequently (although it does appear to be inherently less secure than other browsers)
Make sure that 3rd party cookies are disabled, so that you only receive cookies from the site you are visiting, and not those from 3rd party advertisers.
Don't visit porn sites or sites offering free software. These are just a hot-bed for malicious software that would almost certainly gain access to your computer without you realising, just by you visiting the site.
You may also find that some sites offering free fonts, free ringtones, free music and free coupons, will also try to infiltrate your computer with various nasties.
In Firefox and Safari for Mac, if you hover your mouse over a link, the web address will appear in the bottom left hand corner of the browser window. Always look here, to make sure the web address shown relates to the link you're about to click.
Scan your system frequently for adware and spyware using any number of free programs.
For Firefox, we love NoScript. It's an add-on that prevents nasty scripts from executing without your knowledge.
And here is a great page describing how best to secure your web browser: http://www.cert.org/tech_tips/securing_browser/#Mozilla_Firefox
It does make browsing slightly more inconvenient, but we firmly believe that you'll get the hang of it very quickly, and it's a small price to pay for a whole lot of extra safety.
PLUS - Keep your software UP TO DATE