Is the forum background lagging? Read this.

[Apoc]

This is an an issue with the latest version of Internet Explorer. Disable smooth scrolling in the options menu to fix this.

[RestrainedRaptor]

On the subject of background images, the current setup to stretch the background image to always fit the viewport height and width can result in undesired stretching if the browser isn't in a 16:9 ratio. Instead of using

background-size: 100% 100%;

use

background-size: cover;

[RestrainedRaptor]

I've implemented the fix in my CSS style that you can find here.