Whilst there's plenty of tools around for helping with CSS
styling, if you want a neat little browser bookmarklet
that displays all the properties associated with the selected element and "box model for any element on any web page", then XRAY
might be just the thing.
XRAY shows you the sizes and other attributes of element you select, fades the rest of the page out and hovers a panel over the page to show the properties. For those of you wanting a quick and easy way to inspect CSS box models, this might be the very thing, and is entirely cross-platform meaning Internet Explorer
derivatives and Safari
users can take advantage of this freebie.