HTML:
<iframe id="mainframe" name="mainframe" style=" 100%; border: none; " scrolling="auto" frameborder="0" src="index.aspx"></iframe>
JS:
window.onresize = function () { changeFrameHeight(); }
$(function () {
changeFrameHeight();
});
function changeFrameHeight() {
var ifm = document.getElementById("mainiframe");
ifm.height = document.documentElement.clientHeight - 56;
}