function doOpenTab ( tab_id ) {
	for ( tabno=0; tabno<visibletabcount; tabno++)	{
		elementID = visibletabs[tabno] + 'Tab';
		var theElement = $(elementID);
		if ( visibletabs[tabno] + 'Tab' == tab_id ) { 
			var setclass = 'active_tab';
			var unsetclass = 'inactive_tab';
		} else {
			var setclass = 'inactive_tab';
			var unsetclass = 'active_tab';
		}
		theElement.addClassName(setclass);
		if ( theElement.hasClassName ( unsetclass ) ) {
			theElement.removeClassName ( unsetclass );
		}
		elementID = visibletabs[tabno] + 'TabContent';
		theElement = $(elementID);
		theElement.addClassName(setclass + 'Content');
		if ( theElement.hasClassName ( unsetclass + 'Content' ) ) {
			theElement.removeClassName ( unsetclass + 'Content' );
		}		
	}
}