have previous and next buttons on top as well in the chat box. When I am browsing the chat history for a friend, I go to the bottom and read upwards to read in sequence, when I reach the top I need to go to the previous page, but the button is at the bottom of the page.. so I scroll down and click.

Also consider making the chat history without pages. One should be able start at the bottom and scroll up continuously till the newest message.