First, thanks for the fantastic plugin.

My question, and a fairly simple one so please forgive me if it is addressed elsewhere:

What is the easiest way to add my own new text label underneath a given input field, similar to the "email required" label that appears underneath an email address input? 

For example, if I wanted to add a text label that reads "optional" underneath the Web site field in the default form, what's the easiest way to go about that?

Thanks!