conf = {
       className : 'rollover',
       postfix : '_on'
};
function setMouseOverMottoImages() {
       var objects01 = $('mottoroll01');
       var objects02 = $('mottoroll02');
       var img01 = $('motto01');
       var img02 = $('motto02');
       changeSrcFunction(img01.src);
       changeSrcFunction(img02.src);
    objects01.onmouseout = changeSrcFunction(img01.src, img01);
    objects01.onmouseover = changeSrcFunction(img01.src.replace(/(\.gif|\.jpg|\.png)/, conf.postfix+"$1"), img01);
    objects02.onmouseout = changeSrcFunction(img02.src, img02);
    objects02.onmouseover = changeSrcFunction(img02.src.replace(/(\.gif|\.jpg|\.png)/, conf.postfix+"$1"), img02);
}

function changeSrcFunction(data, imgObj){
       return function(){ imgObj.src = data; }
}
Event.observe(window, 'load', setMouseOverMottoImages, false);