There are several free pop-up stoppers available.

My favourite is the google toolbar.
Yahoo also offer a free companion which can stop pop-ups.
Pop Up Manager is free for personal use and works in IE 5 + 6.

Browsers such as Mozilla and Opera offer their own pop-up stoppers.
IE add-ons such as Avant Browser & Myie2 also contain popup stoppers along with other features such as tabbed browsing.

Continuous pop-ups could be indicative that you are infected with a virus or malware,
Follow the instructions in the security help page.

Change the settings from your browsers menu bar.
View >>> Text size.

Another setting that can change your font size is:-
Control Panel >>> Accessibility Options >>> Display Tab.
Using "High Contrast" will set the font size large.

It is most likely that your browser has been hijacked.
Follow the instructions in my help page here.

Microsoft have a knowledge based article on how to do this at:- http://support.microsoft.com/default.aspx?scid=kb;EN-US;q318378

Download unbrand.vbs from http://www.dougknox.com/utility/scripts_desc/unbrand.htm