In Gravity Forms 1.5 we’re adding some new “Ready Classes”. Using these new classes, you can easily create more advanced alternative layouts for the fields in your forms.
Essentially, Ready Classes are class names that you can add to the parent element surrounding each field to take advantage of pre-defined styles included in the default form stylesheet.
Get complete details here:
http://www.gravityhelp.com/css-ready-classes-for-gravity-forms/