<script>
function checkAll(){
var e=window.event.srcElement
var o=document.getElementsByTagName("input")
for(i=0;i<o.length;i++)if(o[i].type=="checkbox")o[i].checked=e.checked
}
</script>
function ChkAll(form)
{
for (var i=0;i<form.elements.length;i++)
{
var e = form.elements[i];
if (e.name != 'chekall')
e.checked = form.chekall.checked;
}
}
<input type="checkbox" name="chekall" value="on" onclick="ChkAll(this.form)">