FOR VERSION 3.0.9 OR EARLIER ONLY
If you include Webfonts in your website you will notice that every font service works slighty different when it comes to the italic font style. The good news is that there are only 2 methods.
Method 1 - It's in the font name
If you got a seperate name for every weight and style of your font, most of the time the font style is included in the name so you don't need to edit the font style for italics. Here is an Example: 'Helvetica Neue Light Italic'.
So if your fontname describes the weight and the style, please set 'Font Style' for italics to 'Normal'.
Method 2 - Set the weight and style via CSS
In this case (like on typekit.com) you got always the same fontname and set the weight and the style via CSS. In this case please set the 'Font Style' for italics to 'Italic' if you include a italic font style.