One can use parchment to write messages on it. To do this one should right-click on the parchment in inventory and write on it like on runestone.
The funny thing that if you right-click on parchment and mini-window "write your message" appears, you can't close it(even if you haven't written there anything). Moreover, if you close your inventory and then open it and right-click on the parchment again, you will have two parchment "write your message" mini-windows of which both can not be closed.
Bug happens in default and ender clients.
Sorry for broken english.