I'm not exactly sure what you mean, but to make a window bigger or smaller, you can click and drag the 'resize widget' in the bottom, right hand corner of each window. Clicking and dragging this area while moving the mouse will make the window a size of your choice.
and PS: IE for Mac is discontinued and hasn't been touched for years. Check out using Safari as your web browser (should be built in with all new Macs), it has much better standards support and interface.