Most browsers allow you to make room for the page being viewed by pressing the F11 key. However, apart from the Opera web browser, which is by far the best behaved in this area, most other browsers leave some kind of title or toolbar on screen. You can return the browser to its normal appearance by pressing F11 again.
In fact you can get a true full screen window with most of these browsers even so.
After you press F11, right click on the toolbar that is left across the top. This will show you a context menu, containing an "Auto-hide" option. If this option is not shown with a tick beside it, then click on the option to enable it. Now the browser will be entirely full screen except when you move the mouse to the top of the screen, or to where the task bar would normally appear.
both these browsers leave a toolbar at the top of the screen which you cannot get rid of without installing the auto-hide extension. I recommend installing this extension. Once installed the toolbar at the top behaves similarly to Internet Explorer.
If your Opera browser does not go full screen when you press F11, consider upgrading to the latest release.
Consult the help pages for your browser.