a="";
function anchor(){
document.images.wunder.src = "http://banners.wunderground.com/banner/gizmotimetemp_both/language/www/US/PA/Pittsburgh.gif";
}
<!--
//image preloads
a=1;
b = new Array(2);
b[1] = new Image();
b[1].src = "backgrounds/door.jpg"
b[2] = new Image();
b[2].src = "backgrounds/interior2.jpg"
t = new Array(2)
t[1] = "click door to enter";
t[2] = "click photo to exit";
//-->
function Cat(imgName,select) {a=a+1; if(a>2) a=1;
imgOn = eval(select+".src"); document.images[imgName].src = imgOn;
document.text.txt.value=t[a];
}