Iframe Content Not Rendering Under Scroll In iOs5 iPad/iPhone

OK. found the solution. apparently, the problem appear when the main document height is shorter than the iframe that is scrolled. the parts of the iframe page, that exceed the document height, are not rendered.

So, under my needs, I could solve the problem by adding such a js (with jquery) code:

<script>
$(function() {
     var iframe = $("#myIframe");    
     iframe.load(function() {
         $("body").height(iframe.height());
     });
 });
</script>

If you have an access to iFrame body, apply some transform3d to its content to enable GPU rendering.

In my case adding -webkit-transform: translate3d(0, 0, 0); to main wrapping div did the job.