One of the most used, but under featured HTML controls, is the humble TEXTAREA control. This control is designed to accept large blocks of text from the user. A wide variety of plugins exist for the TEXTAREA that layer it with toolbars, auto-resizing, rich-text editing and the works.
However, for my usage, this was way over kill. I wanted a simple line-number facility that would allow my users easily see where they are. Particuraly handy for editing code online. After searching, I couldn’t find one, so I simply created my own plugin.