Many browsers, including Microsoft's Internet Explorer, have an option to enter full-screen mode. If you're in full-screen mode, your Internet Explorer toolbars and address bar disappear unless you point your cursor at the top of the page. Full-screen mode brings your Web browser to the front of your screen, covering even your Windows taskbar.
Internet Explorer's full-screen mode makes the toolbar at the top of the browser disappear and also covers the taskbar below. If this sounds like your problem, simply press the "F11" key on your keyboard to exit full-screen mode. You can also move your cursor to the screen's upper-right corner and click the "Maximize" box once the toolbar and address bar return.
You may find IE's full-screen mode useful once you know how to turn it off when you don't want it. Full-screen mode is designed to remove all distractions between you and the Web page you're viewing. Many programs have this feature, such as entering full-screen when watching a video. It's simply IE's version, which you may find useful for reading long websites or simply removing distractions and focusing on what you're doing in the browser.
If full-screen mode isn't the issue, you or somebody else who uses the computer may have disabled your toolbar. Fixing this is as simple as clicking "View" from the menu bar, selecting "Toolbars" and choosing the toolbar you'd like to see from the list. The toolbars already displayed feature a check mark next to them. Knowing this, you can also remove any unwanted toolbars, like toolbars that programs on your computer have installed.
If the issue persists, malware may be the culprit. While not necessarily a virus, malware is a broad term used to describe malicious software including viruses, adware, spyware and other computer threats. Make sure your computer's antivirus software is up to date and run it. If it doesn't detect anything, malware protection software may catch something that flew under the antivirus program's radar. Anti-malware protection software is available freely online.