Microsoft Visio 2010 Viewer allows anyone to view Visio drawings and diagrams (created with Visio 5.0 through Visio 2010) inside Internet Explorer (versions 5 through Web browser. ****The Visio 2010 Viewer has all the functionality of the previous viewers, and includes all the security fixes.
Visio Viewer enables users to discover the advantages of using Visio drawings, charts, and illustrations in a Web-based environment. You can view Visio drawings files with a .vsd, .vss, .vst, .vdx, .vsx, or .vtx extension) in Windows Explorer. Internet Explorer will open, and Visio Viewer will render the drawing in the browser window.
Changes in Visio 2010 – Highlights new features in Visio 2010