Quit Safari, then control-click on its icon in the Finder and pick Show Package Contents from the pop-up menu, then navigate to Resources » English.lproj. Duplicate the file Browser.nib, and keep the copy in case all goes wrong and you need to revert to it. Open Browser.nib (Developer Tools required; if they're installed, Browser.nib should open in Interface Builder. If it won't open, you'll need to install the Developer Tools from your original DVD or download them from Apple.)
Select Tools » Show Inspector, then click once on the item in the main window called TabBarView and select "hidden" in the Attributes Inspector window. Click once on the main window where you would expect to see your web pages loaded, and under Size in the Inspector window, change the value "height" to 532. The window now covers the TabBarView. Do not try deleting TabBarView; it can stop Safari from launching.
Save the Browser.nib, quite Interface Builder, and re-launch Safari.

