How can I really see what font the element is using?

When I look on the font-family of an HTML element (from js, firebug or similar) it's always a list. How can I see which of the font is actually used from the list?

How can I tell what font is used in CSS?

Use Chrome Browser Inspect Tool Hover your cursor over the font that you want to identify and right click. Select inspect. This will toggle a panel that will show you all of the code, CSS, and additional features that go into creating this website. Beneath all the HTML code is the styles tab.

Is there an app to tell me what font something is?

Identify fonts in a snap! Take a photo of a design you love - WhatTheFont recognizes the fonts and shows font matches. Great for designers, crafters, and anyone who loves typography.

I realise it's not ideal, but you can copy the text from the viewport and paste it into a rich text editor, and it will tell you.