You have to change the screen resilution on you imac. Should be under control pannel or display options.

If this happens with most web pages, your screen resolution could be too low. "You can change the resolution of your monitor to zoom in for detail work or to zoom out and see a whole page or more at a time. To change your screen resolution, follow these steps: 1. Select the Monitors control panel from the Apple menu, it may also be called Monitors and Sound. Note: If you have more that one monitor, a separate Monitors control panel will appear on each display. 2. Click on the resolution you desire in the Resolution section of the control panel. 3. The new resolution will be displayed after you select it. 4. Close the Monitors control panel by clicking the close box in the upper-left corner. 5. If the image is distorted, adjust the video controls in the Monitors control panel or on the monitor itself." Source and further information: http://support.apple.com/kb/TA21610?viewlocale=en_US Some Web pages are actually broader than the standard size. I think they are supposed to be displayed on a large screen with high resolution. It is a little annoying to display them on a normal screen. If you don't have such a large screen you won't necessarily get an advantage from increasing the screen resolution, because the characters could become too small to be read easily.