A term coined by MacroMedia for their DreamWeaver application. It means that if you import a webpage from another application, the source HTML will not be overwritten or changed in any way. While most editors have this feature now, it was unique when the first version of DreamWeaver was released. The earlier versions of Microsoft FrontPage were infamous for reformatting imported HTML, and Macromedia's Roundtrip HTML was used as a selling point to the (understandably) frustrated web developers.