my hotmail screen print has minimalized, how do I return it to normal size 10 ?

I was typing a message then 'keyed Control B' [I think?] and the whole of the HOTMAIL screen's print shrunk down to  about a font size '6' instead of the normal size on the screen.  This includes all the Inbox and folders and all the messages which are barely readable being so small.

how can I get it back up to the NORMAL SIZE ? hope someone can give me the answer ?