Properties Panel missing

The side panel where I can assign materials and such closed somehow, and I have no idea how to reopen it.
How can I get it back?

The panel I am talking about is the one marked in red here http://i.imgur.com/K9CLEpI.png

The side panel where I can assign materials and such closed somehow
Show us

Save your file, use File / Load Factory Settings menu entry, then open your saved file ensuring you disable the ‘Load UI’ option
or
If you have set your 3d view to full screen change it back with Ctrl+Up arrow or the ‘Back to Previous’ button at the top of the window
or
Split your 3d view vertically and change one on the 3d views to a properties window. See http://screencast.com/t/H62SwfVi3

I did this, and now all is good, thank you.