Alt CSS

Alternate CSS Style Selector allows you to set an alternate style on pages which provide one

Alternate CSS Style Selector (ACSS for short) provides an interface to choose from alternate stylesheets which are provided by some sites. When an alternate stylesheet is available an icon will appear in the omnibox, which you can click to see a list of styles to choose from. After choosing a style, ACSS will remember it until you choose another. This extension does _not_ provide user.css capabilities; it's not "Stylish for Chrome". It provides functionality similar to that of Firefox's View, Page Style menu, which isn't present in Chrome. Unfortunately, because javascript is loaded after CSS, the styles may flicker a bit (depending on various factors). I don't think there's any way to fix this at the moment. The "Base (ACSS)" style is all the stylesheets without a title or rel=alternate; the other styles are "Base (ACSS)" plus some extra. "None (ACSS)" disables all styles.