One of the minor bugs which has bothered me for some time in the Sitecore Content Editor is mouse scrolling in the ribbon is backwards, particularly when compared to the ribbon in Microsoft Office products. Scrolling down should progress through the tabs to the right, while scrolling up should progress to the left.

The opposite is what actually happens.

Fixing this issue is actually quite simple. From the Website directory, open /sitecore/shell/Applications/Content Manager/Content Editor.js and change line 252 (within scContentEditor.prototype.ribbonNavigatorWheel) from:

var delta = (evt.wheelDelta > 0 ? 1 : -1);
                            ^

to:

var delta = (evt.wheelDelta < 0 ? 1 : -1);
                            ^