Checkbox style - CSS & js
Css and javascript are common in page style, but ocassionally someone will want to customize form elements. Although radio buttons and checkboxes are awkward to style, it is possible. Some solutions involve changing a span which encloses the form element, others rely on background images.
Be sure to test cross brower appearance. Although it is possible to change the look of the form check boxes, unless there is some overwhelming need, it probably introduces unnecessary complication in the form.
Below are the check boxes as they are seen in IE6, which uses the Fancy Form css for everything.

In Firefox 3, the individual spans respect the styles one by one.

For an article on the ways different browsers render css in form controls see http://www.456bereastreet.com/lab/styling-form-controls-revisited/checkbox/
To download the Fancy Form code, go to http://lipidity.com/fancy-form/