What probably has happened is that you have made the taskbar extra long by moving the "Dotted Line" too far to the right. To fix this, you will need to grab the bottom dotted line by using your left mouse button and move it up and closer to the left on the top. This will, in effect, make the Quick Launch bar shorter. Once you have moved the dotted line, you should be able to shrink the taskbar back to normal size.