Another tool to help you with web development. You would prefer this rather than firebug to exactly see the Box Model of the element you click on. Firebug does not display right away the height, width of the element (only the specified height/width is displayed).

Right now, XRAY is available only on Mozilla browsers and Safari and Internet Explorer version is coming soon, while the Opera version is coming sooner. The best part is it is a bookmarket.

The not-so-good part being you cant use firebug and XRAY at the same time! The javascript and added elements will make Firebug a lot harder.