Xfce can be customized in many different ways. This allows you to personalize the desktop environment to look the way you want it.
The first thing that you should check when Raspbian boots to the desktop is whether the resolution your Raspberry Pi is using is suitable for your monitor. Raspbian attempts to select the correct resolution on your TV or monitor to make sure that everything looks like it should, but sometimes it is unable to do this correctly. You will be able to recognize that the resolution is wrong if the image on the screen looks blurry or doesn't fit properly.
You can change the resolution to suit your monitor using the Monitor Settings application in the preferences section.
Monitor settings
It might take a few goes to find the best resolution for your monitor or TV, but it is definitely worth it! You are also able to customize the refresh rate of your monitor if you still have problems getting the display looking...