toggle.js

function getRealDisplay(elem) {
    if (elem.currentStyle) {
		return elem.currentStyle.display;
	} else if (window.getComputedStyle) {
		var computedStyle = window.getComputedStyle(elem, null );

		return computedStyle.getPropertyValue('display');
	}
}

function hide(el) {
	if (!el.getAttribute('displayOld')) {
		el.setAttribute("displayOld", el.style.display);
	}

	el.style.display = "none";
}

displayCache = {};

function isHidden(el) {
	var width = el.offsetWidth, 
        height = el.offsetHeight,
		tr = el.nodeName.toLowerCase() === "tr";

	return width === 0 && height === 0 && !tr ?
		true : width > 0 && height > 0 && !tr ? false :	getRealDisplay(el);
}

function toggle(element) {
    var el = document.getElementById(element);
	isHidden(el) ? show(el) : hide(el);
}


function show(el) {

	if (getRealDisplay(el) != 'none') return;

	var old = el.getAttribute("displayOld");
	el.style.display = old || "";

	if ( getRealDisplay(el) === "none" ) {
		var nodeName = el.nodeName, body = document.body, display;

		if ( displayCache[nodeName] ) {
			display = displayCache[nodeName];
		} else {
			var testElem = document.createElement(nodeName);
			body.appendChild(testElem);
			display = getRealDisplay(testElem);

			if (display === "none" ) {
				display = "block";
			}

			body.removeChild(testElem);
			displayCache[nodeName] = display;
		}

		el.setAttribute('displayOld', display);
		el.style.display = display;
	}
}