ua = new function() {
    var u = navigator.userAgent, d = document;
    this.ie = typeof d.all != "undefined";
    this.ns4 = typeof d.layers != "undefined";
    this.dom = typeof d.getElementById != "undefined";
    this.safari = /Safari/.test(u);
    this.moz = /Gecko/.test(u) && !this.safari;
    this.mie = this.ie && /Mac/.test(u);
    this.win9x = /Win9/.test(u) || /Windows 9/.test(u);
    this.o7 = /Opera 7/.test(u);
    this.supported = (typeof d.write != "undefined") 
                     && (this.ie || this.ns4 || this.dom);
};

function toggleBike(id, naviOver, bike) {

	// update navi
	document.getElementById(id).src = naviOver; 

	if (ua.ie && !ua.mie) {
		// update bike on picture
		document.getElementById('bikeMouseOver').style.filter = 'progid:DXImageTransform.Microsoft.AlphaImageLoader(src=\'' + bike + '\', sizingMethod=\'scale\')';
	} else {
		document.getElementById('bikeMouseOver').src = bike;
	}
}