function remove_negative_text() {
		var source_elements = document.getElementsByTagName('input');
		// debug(source_elements.length);
		for (var i = 0; i < source_elements.length; i++) {
			if (hasClass(source_elements[i], 'button')) {
				source_elements[i].value = '';
			}
		}
	}
	
	function hasClass(ele,cls) {
		return ele.className.match(new RegExp('(\\s|^)'+cls+'(\\s|$)'));
	}
	 
	function addClass(ele,cls) {
		if (!this.hasClass(ele,cls)) ele.className += " "+cls;
	}
	
	function removeClass(ele,cls) {
		if (hasClass(ele,cls)) {
			var reg = new RegExp('(\\s|^)'+cls+'(\\s|$)');
			ele.className=ele.className.replace(reg,' ');
		}
	}
	
	window.onload = function() {
		remove_negative_text(); // ideally, this should be moved to a template file.
	}

	function debug(s) {
		var mydebugelement = 'my_debug_div';
		if (!document.getElementById) { 
			return false;
		}
		var o = document.getElementById(mydebugelement);
		if (!o) {
			o = document.createElement('div');
			o.id = mydebugelement;
			// t = document.createTextNode(s);
			// d.appendChild(t);
			document.getElementsByTagName('body')[0].appendChild(o);
		}
		
		o.innerHTML += '<div style="padding: 12px; background: #eee; margin: 4px; background: #ffffff; border: 1px solid #333;" class="item">' + s + '</div>';
	}