Fixed scrolling performance issues on Webkit based browsers. (Opera, Chrome, Safari)

Update theme.less

Rebased and added markus101's changes.

src/UI/Content/theme.less

@@ -125,9 +125,9 @@ a, .btn {
 }
 
 body {
-  background    : url('../Content/Images/background/logo.png') 50px center no-repeat fixed, #272727;
-
-  margin-bottom : 100px;
+  background       : url('../Content/Images/background/logo.png') 50px 75px no-repeat;
+  background-color : #272727;
+  margin-bottom    : 100px;
   p {
     font-size : 0.9em;
   }
@@ -297,4 +297,4 @@ dl.info {
   .pull-right();
   position : relative;
   width    : 0px;
-}
+}