See this - http://social.technet.microsoft.com/Forums/windows/en-US/7241ee9a-2592-48b5-9d2b-a3956b69c59d/how-to-display-timedate-on-bottom-task-bar-windows-7 - that's a Windows 7 support issue.

Does this problem occur when the window is maximized or when it is resizable? Either way, the Firefox window should not ever appear in front of the Windows Task Bar unless you are in full screen mode (F11 switches full screen mode on and off).

If the Firefox window is too big, could you try Firefox's Safe Mode? That's a standard diagnostic tool to bypass interference by extensions (and some custom settings). More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled

In the dialog, click "Start in Safe Mode" (not Reset)

Any difference? If that works better, it could indicate a conflict with an extension, or a corrupted toolbar customization file (which also stores window dimensions).

Do you mean the date and time on the Windows Task bar or via an extension in Firefox on the Add-ons bar?

For the Windows Task bar to be visible, you can check its properties to see if the Task bar is visible all the time.

You can make the Add-ons bar appear in Firefox via Ctrl+/.

• Firefox menu button > Options
• View > Toolbars (press F10 to display the menu bar)
• Right-click empty toolbar area