var checkIdPostfix = '_chck';
var checkedCls = 'checkbox-checked-image';
var uncheckedCls = 'checkbox-unchecked-image';

window.addEvent('domready', function() {	
	var elems = $(document.body).getElements('div');
	
	for (i = 0; i < elems.length; i++) {
		if (elems[i].className == checkedCls || elems[i].className == uncheckedCls) {
			elems[i].addEvents({
			    'click' : function() {
					if (checkedCls == this.className) {
						document.getElementById(this.id + checkIdPostfix).checked = false;
						this.className = uncheckedCls;
					} 
					else {
						document.getElementById(this.id + checkIdPostfix).checked = true;
						this.className = checkedCls;
					}
				}
		    });
		}
	}
});