function _disable_after_click(event) {
	if(this._clicked) {
		event.preventDefault && event.preventDefault();
		event.returnValue = false;
		return false;
	} else {
		this._clicked = true;
		return true;
	}
}
function disable_buttons_after_use() {
	var inputs = document.getElementsByTagName('input');
	var buttons = document.getElementsByTagName('button');
	for(var i = 0; i < inputs.length; i++) {
		var el = inputs[i];
		if(el.type == 'submit' || el.type == 'image') {
			el.onclick = _disable_after_click.bindAsEventListener(el);
		}
	}
	for(var i = 0; i < buttons.length; i++) {
		var el = buttons[i];
		if(el.type == 'submit') {
			el.onclick = _disable_after_click.bindAsEventListener(el);
		}
	}
}