I have a webpage with 2 iFrames in it. Both of them are with fixed width and height. I am loading external websites inside them. How can I resize those external websites width to fit with the iFrame (like mobile browsers does by changing viewport)?
What you can do is set specific width and height to your iframe (for example these could be equal to your window dimensions) and then applying a scale transformation to it. The scale value will be the ratio between your window width and the dimension you wanted to set to your iframe.
E.g.
<iframe width="1024" height="768" src="http://www.bbc.com" style="-webkit-transform:scale(0.5);-moz-transform-scale(0.5);"></iframe>