function getElementsByClass( searchClass, domNode, tagName) { 
	if (domNode == null) domNode = document;
	if (tagName == null) tagName = '*';
	var el = new Array();
	var tags = domNode.getElementsByTagName(tagName);
	var tcl = " "+searchClass+" ";
	for(i=0,j=0; i<tags.length; i++) { 
		var test = " " + tags[i].className + " ";
		if (test.indexOf(tcl) != -1) 
			el[j++] = tags[i];
	} 
	return el;
} 
function showtab(tabname) 
{ 
	// hide every element with class 'tab'  
	var tabs = getElementsByClass('caption');
	for(i=0; i<tabs.length; i++) 
		tabs[i].style.display = 'none';
	// hide every element with class 'tab'		 
 
	document.getElementById(tabname).style.display='block';
	// show element with given tabname 
}