var interval1 = null;
function change_opacity(elem, step, frequency) {
	if(typeof window.getComputedStyle == "undefined") {window.getComputedStyle = function(element, pseudoElement) {return element.currentStyle;}}
	var elem_cs = window.getComputedStyle(elem, null);
	var elem_opacity = parseFloat(elem_cs.opacity);
	interval1 = setInterval(do_change_opacity, frequency);
	function do_change_opacity() {
		if(elem_opacity > -0.1 && elem_opacity < 1.1) {
			elem_opacity = elem_opacity + step / 100;
			elem.style.opacity = elem_opacity;
		} else {clearInterval(interval1);}
	}
}
function fix_opacity() {
	clearInterval(interval1);
}