/**
 * selects all checkboxes with messages on the page
 * @param bool checkbox status, true - a checkbox will be checked,
 *  false - a checkbox will be unchecked
 */
function selectAllMessages(checkVal)
{
	var fObj = document.forms['messagesForm'];
	for (var i=0;i<fObj.elements.length;i++) {
		var e = fObj.elements[i];
		if ( (e.name.search(/threadIds/) != -1) && (e.type=='checkbox') && (!e.disabled) ) {
			e.checked = checkVal;
		}
	}
}