Hide Tab using JScript

//CRM 4.0
crmForm.all.tabIndexTab.style.visibility = "hidden";

// CRM 2011
Xrm.Page.ui.tabs.get(TabIndex).setVisible(false);
Xrm.Page.ui.tabs.get(TabIndex).setVisible(true);
//Or
Xrm.Page.ui.tabs.get(TabName).setVisible(false);