The next best thing is to have a system spring cleaning at least once a week, or every couple of days for heavy users. Run an anti-virus scan, anti-spyware software like Spybot and Adaware, keep your firewall up to date and generally be alert for intruders onto your system.
Most of the programs can be set up to run automatically, so once you have configured them, they update themselves and run without you needing to do anything.
As browsers have moved on, there are add-ons you can install into them. These add extra functionality like weather pop-ups, instant messaging within the browser and other tools. These can also cause a CPU to go to 100% as they aren’t always written properly. They are designed by talented enthusiasts who mean no harm, but sometimes don’t get everything completely right.
If you use add-ons in your browser, and the CPU goes to 100%, try disabling add-ons one at a time to see if one of them is overworking your processor.
By following these steps, you should prevent problems when surfing the Internet. A processor that hits 100% occasionally is nothing to worry about, one that stays there is.