Source: http://lifehacker.com/5940943/swiftpreview-automatically-previews-links-when-you-hover-over-them
Chrome: If you want to quickly glance at a link within a news article but don't want to click on it, SwiftPreview is a simple way to do it. When you hover over a link, SwiftPreview shows a graphic preview of the page linked, and the extension is fully customizable so you can keep it from being annoying.
Right after you install SwiftPreview you're offered up a set of options to customize it. You can change the preview size, scaling, and block domains. You can also change its behavior so it only shows previews when you hold the shift key instead of every time you hover over a link. SwiftPreview is handy for avid news hounds that might want to get the rundown of a linked page without actually opening it up.
SwiftPreview | Chrome Web Store