Microsoft Internet Control (Browser Control)...

Hello.
I'm currently at a project called Quick HTML Editor that contains two tabs named HTML (Editor) and Preview. For preview tab, I have used Browser control (IE. I'm using later version Probably 7th or 8th). And the problem is when the application is used with the computer having earlier version of IE (6.0 and others) the application shows some errors. Actually, I was reported by my friend whom I gave this application to test. So, what can be done as solution for the problem??