Wrap it inside a function.
<script type="text/javascript"> window.onload = function(){ setInterval(div_show, 10); } </script>
Also, if you're sure if you want to execute this function only once when the body loads, you might as well want to use setTimeout instead of setInterval. Like
<script type="text/javascript"> window.onload = function(){ setTimeout(div_show, 10); } </script>
If you want 10 it to execute after 10 seconds, you need to set the timer parameter to number of seconds * 1000 In your case, 10*1000
Either
setTimeout(div_show, 10*1000);
or
setTimeout(div_show, 10000);
window.onload=function(){ setInterval(div_show(), 10); };()---window.onload=function(){ setInterval(div_show, 10); };