Hide a tab
Hiding a tab is not supported by Microsoft. Although unsupported due to the fact teh tab order could change using some undocumented features aren't always a bad thing to do. If you clearly define to your client that this is unsupported and for this reason it's up to them to decide whether or not to do it. This is one of these unsupported functions that I do routinely to hide tabs the user doesn't want displayed for their business processes.
// Hide the third tab
crmForm.all.tab3Tab.style.display="none";