I've been handed a few Adobe Illustrator to turn into web pages and it seems like Adobe Illustrator CS3 doesn't do measurements in in pixels by default. Is there a way to take measurements in pixels in Adobe Illustrator CS3 or do I need to export them?
Illustrator is a vector graphics program ... meaning that it works with mathematical descriptions of lines/shapes/text etc, rather than dots, so until you export to a raster/bitmap format, it's not locked into any particular pixel resolution. In fact that's why they call vector graphics "resolution independent".
But if you decide up front you're going to export at, say, 100dpi, then you know that each inch (in your AI graphic) will export to 100 pixels. 1/100 inch = 1 pixel.