Use larger font for column numbers.
Change the background color of column numbers.

Also remove shadow around row numbers.
Improve the appearance of bars for accessing the data panel.
Delete a redundant CSS property.
Add locking function.
Hide prev/next buttons on the ends.
Use 'disabled' CSS class for showing/hiding #lock.
Add functions lock() and unlock().
Store the lock state as a part of a resume data.
Add a function save_state().