function tgiShowHide(elem) {
	var e;
	if (document.layers) { /* NS 4.x */
		e = document.layers[elem]; 
		e.visibility = (e.visibility == "hide") ? "show" : "hide";
	} else {
		if (document.getElementById) { /* DOM-compliant browsers */
			e = document.getElementById(elem);
		} else if (document.all) { /* IE 4.x */
			e = document.all[elem]; 
		} else {
			return /* unidentifiable: no action */
		}
		if (e.style.visibility == 'hidden'
			|| e.style.visibility == 'undefined'
			|| e.style.visibility == '') {
			tgiHideAllClass('callout'); /* hide all of the 'callout's */
			e.style.visibility = 'visible';
		} else {
			tgiHideAllClass('callout'); /* hide all of the 'callout's */
			e.style.visibility = 'hidden'; /* hide the particular, just in case */
		}
	}
}

function tgiHideAllClass(c) {
	var re = new RegExp (c);
	var divs = document.getElementsByTagName('div');
	for (var i = 0; i < divs.length; i++) {
		if (divs[i].className && re.test(divs[i].className)) {
			divs[i].style.visibility = 'hidden';
		}
	} 
}