function up(){
var iup=demo.scrollTop;
var iup1=demo.scrollTop;
while (iup>iup1-210) {
iup=iup-5;
demo.scrollTop=iup;
}}
function down(){
var iup=demo.scrollTop;
var iup1=demo.scrollTop;
while (iup<iup1+210) {
iup=iup+5;
demo.scrollTop=iup;
}}