Cons of using Internet Explorer's Compatibility Mode

Question

What are cons of force a web site viewed in IE to compatible mode? Say we force IE9 to IE8 compatiblity mode?

• Performance drawbacks
• C

Answer 1

You cannot say you have tested in IE6/7/8/9 until you have tested in those different versions. Emulating the test environment is not the same as using the test environment. To my knowledge IE7/8 compatibility modes are the older render engines, not the underlying browser as a whole, bugs and all. It is closed source so you will never know.

Convert Microsoft's free to download virtual disk images for cross-browser testing to Virtualbox images and put them on a machine that just runs Virtualbox. An old machine will do, run the VMs headless and access them with remote desktop. In that way you will be able to test in all browsers without burdening your machine with MS/Spyware.