I noticed that in any IE browser, the content div is slightly wider than the container.

This occurs only when the content area is in DIV mode and Auto Resize is set to true.

I attached a screen shot from the demos site.

Hi Michael,

I can verify that this is a known issue that originates from the resize functionality of the RadEditor control. This feedback portal item has been created for this bug item. You could track the task's progress with it, vote or comment about it. 

Due to the complexity of this matter I am unable to provide a firm estimation for when is going to be fixed. Also I cannot suggest any possible workaround until it is resolved.  

Regards,
Ianko
Telerik