This has been reported before but not with current Version of CF11 Update 3 and Firefox 35.0. Using Firebug creates a long delay and brings up the warning:
Relative positioning of table rows and row groups is now supported. This site may need to be updated because it may depend on this feature having no effect. http://localhost/CFIDE/scripts/ajax/ext/ext-all.js Line 18
Is there any way to get rid of the delay?