how to set a maximum length for text area in rails

About the time that shiva shiva posted four very, VERY basic questions within an hour or so which seemed to indicate he [or she] needed something a little more comprehensive than a simple reply about how to solve one question. I really did mean it helpfully. Heck, I ask a hell of a lot of questions sometimes. Moreso in the #rubyonrails channel but whatever. I know sometimes you really do need to RTFM. :confused: