First of all, which iBook: clamshell or white? If it's clamshell, it can only go up to 800x600. Second, what OS: OS 9 (Classic) or Mac OS X? If it's OS X, you should not be using Internet Explorer. Use Safari or Firefox. IE has not been updated in years and probably doesn't work well with a lot of web sites. I'm guessing OS 9 because you mention the Monitor control panel instead of Displays preferences. I'd update to OS X if you can.
Steve