From :
http://georepository.com/crs_3785/Popular-Visualisation-CRS-Mercator.html
"Popular Visualisation CRS / Mercator is a projected CRS last revised on 03/14/2008 and is suitable for use in World between 85°S and 85°N. Popular Visualisation CRS / Mercator uses the Popular Visualisation CRS geographic 2D CRS as its base CRS and the Popular Visualisation Mercator (Mercator (1SP) (Spherical)) as its projection. Popular Visualisation CRS / Mercator is a CRS for Certain Web mapping and visualisation applications. It was defined by information from Microsoft.. Uses spherical development. Relative to an ellipsoidal development errors of up to 800 metres in position and 0.7% in scale may arise. Some applications call this WGS 84. It is not a recognised geodetic system: see WGS 84 / World Mercator (CRS code 3395)"