We may need a little more info from you.
What OS are you running? I ask, because your profile says OS 10.6.8, which only runs on Intel-Based Macs, and this particular forum is for PPC (G3,G4,G5) iMacs, and the latest OS the most advanced of these iMacs can run is OS 10.5.8.
Click on the Apple in the upper left corner of the screen, pull down and click on About This Mac. A window will open and say 'Mac OS X, Version 10.x.x. Processor: blah-blah-blah: RAM: X GB Blah-Blah. Please provide what OS version, what Processor, and the amount of RAM. Then click the More Info button. Highlight Hardware at the top left of the new window, and copy down what the Model Identifier is.
Now, open Safari, and click the spinning wheel in the address bar to stop loading the webpage. Click on Safari in the Menu Bar, pull down and click on About Safari. What version of Safari are you using?
Wen you bought the iMac, did they give you the original OS Install disks, or a retail version of the OS X you are using?
Have you tried emptying the cache and cookies from Safari? Have you tried restarting the computer? Resetting the PRAM? Have yo tried a browser like Firefox or Chrome? Have you tried the Software Update to see if you have the latest updates for your OS and Safari?
Those are a few things I can think of to try before you respond back.