function disableclick(e) {
    if (document.all) {
        if (event.button==2||event.button==3) {
            if (event.srcElement.tagName.toUpperCase()=="IMG"){
                alert(clickmessage);
                return false;
            }
        }
    }
    else if (document.layers) {
        if (e.which == 3) {
            alert(clickmessage);
            return false;
        }
    }
    else if (document.getElementById) {
        if (e.which==3 && e.target.tagName.toUpperCase()=="IMG") {
            alert(clickmessage);
            return false;
        }
    }
}
function associateimages() {
    for(i=0;i<document.images.length;i++)
        document.images[i].onmousedown=disableclick;
}

var clickmessage="Right click disabled on images!";

function disableImageRightClick() {
    if (document.all)
        document.onmousedown=disableclick;
    else if (document.getElementById)
        document.onmouseup=disableclick;
    else if (document.layers)
        associateimages();
}