function el(id) {
	if (document.getElementById) {
		return document.getElementById(id);
	} else if (window[id]) {
		return window[id];
	}
	return null;
}

function checkall(cbox, newstate) {
    for (i = 0; i < cbox.length; i++) { cbox[i].checked = newstate; }
}

function init_checkbuttons() {
	var btndiv = el("checkbuttons");
	if( ! btndiv ) { return; }
	var btn1 = document.createElement("input");
	btn1.type = "button";
	btn1.value = "Check all";
	btn1.onclick = function() { checkall(this.form.t, true); };
	btndiv.appendChild(btn1);
	var btn2 = document.createElement("input");
	btn2.type = "button";
	btn2.value = "Clear all";
	btn2.onclick = function() { checkall(this.form.t, false); };
	btndiv.appendChild(btn2);
}

function init() {
	init_checkbuttons();
}

window.onload = init;