Hi,
You can look at this form template I made. The errors are shown on top as well as highlighted inline.
http://cvs.openacs.org/cvs/*checkout*/openacs-4/contrib/packages/bcms-ui-base/resources/form-template.adp?rev=1.2
It does use css, you can look at the style here:
http://cvs.openacs.org/cvs/*checkout*/openacs-4/contrib/packages/bcms-ui-base/www/bcms-ui-base-style.tcl?rev=1.1
The style that you will want are between the comments "form template styles".