Complex sentence: CoolPreviews, formerly known as "Cooliris Previews", is a web browser plugin for Mozilla Firefox, Internet Explorer, Safari, and Flock that opens a preview of the underlying content of a web link when the mouse hovers over the link.
Split into simpler sentences: CoolPreviews, formerly known as "Cooliris Previews", is a web browser plugin for Mozilla Firefox that lets user preview pages from weblinks. The plugin opens a preview of the underlying content of a web link when the mouse hovers over the link.