QUOTE
Zoom in: Many browsers and other applications give you advanced features with your wheel. For example, in Internet Explorer, hold Ctrl and rotate the mouse wheel forward or backward to decrease or increase the size of text in Web pages. If this doesn't work in your copy of IE, choose Tools, Internet Options and click Accessibility on the General tab. Check Ignore font sizes specified on Web pages and click OK twice. To get this effect in Mozilla, choose Edit, Preferences, double-click Advanced (or click the + sign next to it), and then click Mouse Wheel. Select the tab for the key (Alt, Control, Shift, or No modifier key) that you want to hold down when adjusting text size, and then click Make the text larger or smaller. Click OK.
This trick works even better in recent versions of applications like Microsoft Word, Adobe InDesign CS, and the Opera browser (free to try, $39 to keep). In these apps, <Ctrl>-wheeling enlarges or reduces the magnification level of your entire page (including graphics) rather than just adjusting the text display size (sweet!). InDesign zooms in on the area under your pointer, letting you magnify a specific spot just by pointing and wheeling. And Opera lets you return your Web page to its default '100%' view by Ctrl-clicking the wheel once.
In Adobe Photoshop CS, hold Ctrl and the spacebar while clicking to zoom in, or press Alt and the spacebar while you click to zoom out. But with the mouse wheel, just hold either key combination (Ctrl-Space or Alt-Space) as you wheel forward or back to zoom in or out on the spot under your pointer.
quoted from
http://www.pcworld.com/howto/article/0,aid,117821,00.asp