function id(x) {
    if (typeof x == "string") return document.getElementById(x);
    return x;
}

function loadImageRollover(targetImage, normalUrl, rolloverUrl)
{
    //preload rollover image
    (new Image()).src = rolloverUrl;

    targetImage = id(targetImage);

    targetImage.onmouseover = function() {
	targetImage.src = rolloverUrl;
    }
    targetImage.onmouseout = function() {
	targetImage.src = normalUrl;
    }
}
	    

function loadLocalRollover()
{
    loadImageRollover("SmartTetherScreenCapture",
		      "image/SmartTetherGraphCapture.png",
		      "image/SmartTetherDataCapture.png");
}

if (window.addEventListener) {
    window.addEventListener("load", loadLocalRollover, false);
}
else if (window.attachEvent) {
    window.attachEvent("onload", loadLocalRollover);
}