Desktop still visible when using browsers

When opening Firefox or Internet Explorer I can still see a small portion of the desktop showing right above the taskbar. I've tried dragging the screen to cover it up, but I seem to be unable to do that. Both browsers are maximized, but the small strip is still visible.

I've included a screenshot (Right above the taskbar you can see part of my desktop wallpaper showing).

Enlarge the taskbar back to defalt, then open Firefox or whatever then close FF and set the taskbar to how you like it and then try again.

Thank you very much, it worked.