Building an Gmail "Compose Mail" editor

Hi, when you compose a new mail in Gmail you can format your message using some cool formating tools (bold, italic, underline, hightlight color, etc).
I'm starting a project and wnat to build a message editor like that in Gmail.
Need some directions in start searching for html, css, javascript technics I'll need to do this.

P.S.: this body editor here in Experts-Exchange has some tools I'll need (like bold, italic, etc) but, as I coud see, it put tags in the message... Gmail editor is more like I'm looking for because it doesn't put tags on the message. It shows the formated text in real time instead.

thanks