function preload(images,prefx) {
        for (i =0;i<images.length;i++) {
                img = images[i];
                eval(img+"1 = new Image();\n"+img+"1. src='"+prefx+img+"1.gif';\n");
                eval(img+"2 = new Image();\n"+img+"2. src='"+prefx+img+"2.gif';\n");
        }
}
function roll(img,sores) {
        eval("document.images."+img+".src = "+sores+".src;");
}
function unroll(img) {
        eval("document.images."+img+".src= "+img+".src;");
}