Hiding a section using java script in MS CRM 4.0

Hidding a section which contains an IFrame :
var sec = document.getElementById( "tab5"  );
            sec.childNodes[0].rows[ 1 ].style.display = 'none';
           


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Hiding a section with attributes on it :


crmForm.all..parentElement.parentElement.parentElement.style.display='none';