Go to System preferences in the Dock, then to Accounts. There is a lock down at the left. Click on it, it will ask for your login password, input, hit OK. The lock will open. Press the plus sign above the lock. In the window enter a new account name (anything) and a new password (easy to remember). Click on allow this user to administer the computer (in Lion this option is on top as an option between guest and administrator). After you are done, log out (under Apple sign, top left of the screen. On the login screen, you will now see two options: one is your main account, the other is the new one. Click on the picture of the new one and in the window enter new password. The computer will be now the new account. In the Dock, open Safari and see if the site works. Chances are that it will. Then you can log out again and log in under standard account. This account now needs maintenance, like repairing permissions, checking disk, emptying caches, updating Flash player, etc. You can use Disk Utility (included), TinkerTool System (shareware). If you have an install disk, boot from it (put in the tray, restart with key "c" on the keyboard pressed and then hit "repair disk" from the disk utility. But this may be done later. Now we need to find out if the problem is with the main account only or systemwide.