Using a font name with spaces in a inline style requires wrapping the name in 's. The single ' in the font name also needs to be wrapped in 's.
In a stylesheet, you would use " but an inline style mandates the '.
Code:
<h2 style="text-align: center; font-family: 'Gabriel Weiss''' Friends Font', sans-serif;">Content</h2>
I would suggest simply using <h2> and the following in a CSS stylesheet linked to your text file (the 4em font size is simply to allow easily seeing the difference between the CSS and inline style):
Code:
<h2>Content</h2>
<h2 style="text-align: center; font-size: 2.5em; font-family: 'Gabriel Weiss''' Friends Font', sans-serif;">Content</h2>
h2 {
text-align: center;
font-size: 4em;
font-family: "Gabriel Weiss' Friends Font", sans-serif;
}