<body style="margin:0px;padding:0px;overflow:hidden">
<iframe src="http://www.youraddress.com" frameborder="0" style="overflow:hidden;overflow-x:hidden;overflow-y:hidden;height:100%;width:100%;position:absolute;top:0px;left:0px;right:0px;bottom:0px" height="100%" width="100%"></iframe>
</body>#IFRAME_ID {
width: 100%!important;
height: 100%!important;
}
<iframe src="http://www.youraddress.com" id="IFRAME_ID"></iframe>
#####################
If still not working you can try solution from on the solutions from the link
https://stackoverflow.com/questions/819416/adjust-width-and-height-of-iframe-to-fit-with-content-in-it#IFRAME_ID {
width: 100%!important;
height: 100%!important;
}
<iframe src="http://www.youraddress.com" id="IFRAME_ID"></iframe><body style="margin:0px;padding:0px;overflow:hidden">
<iframe src="http://www.youraddress.com" frameborder="0" style="overflow:hidden;height:100%;width:100%" height="100%" width="100%"></iframe>
</body>