function getElementsByClassName(searchClass,tag,node) {
        var classElements = new Array();
        tag = tag || '*';
        node = node || document;
        var els = node.getElementsByTagName(tag);
        var elsLen = els.length;
        var pattern = new RegExp("(^|\\s)"+searchClass+"(\\s|$)");
        for (i = 0, j = 0; i < elsLen; i++) {
                if ( pattern.test(els[i].className) ) {
                        classElements[j] = els[i];
                        j++;
                }
        }
        return classElements;
}

buttons = function() {
	buttons = getElementsByClassName('button', 'a');
	for (var i=0; i<buttons.length; i++) {
		buttons[i].onmouseover=function() {
			this.className+=" button_hover";
		}
		buttons[i].onmouseout=function() {
			this.className=this.className.replace(new RegExp(" button_hover\\b"), "");
		}
	}
}

if (window.attachEvent) window.attachEvent("onload", buttons);