THe ! is freemarker's default value operator. Basically if the variable you're trying to access is null, the value after the ! is used. In this case, there's no value after the !, so the result will be the empty string, an empty hash or empty sequence (probably a string in your case above). See http://freemarker.org/docs/dgui_template_exp.html#dgui_template_exp_missing_default for more detail
