$(document).ready(function(){
	rollOverImage();
});

function rollOverImage() {
    var preLoad = new Object();
    $('img.rollOverImg, input.rollOverImg').not("[src*='_on.']").each(function(){
        var imgSrc = this.src;
        var fType = imgSrc.substring(imgSrc.lastIndexOf('.'));
        var imgName = imgSrc.substr(0, imgSrc.lastIndexOf('.'));
        var imgOver = imgName + '_on' + fType;
        preLoad[this.src] = new Image();
        preLoad[this.src].src = imgOver;
        $(this).hover(
            function (){ this.src = imgOver; },
            function (){ this.src = imgSrc;  }
        );
    });
}