The default skin, SmoakyMain, is design for screens resolutions of at least 1024x768. If you are one of the very few that uses resolutions of 800x600 or smaller you will experience the issue above (horizontal scrolling). In these cases you will want to choose the SmoakyMainSmall skin. It is a condensed version of the main skin and should alleviate the horizontal scroll problem.
To change skins:
Use the Skin Selector drop down menu, found in the extreme bottom left corner of the forums, to select a skin to use.