If looking at the HTML doesn't help, then you may need to look at the style sheet.
At the top of the HTML source may be a link starting something similar to:
Code:
<link rel="stylesheet" href="style/style.css"...
What you'll need to do then is change the address in your browser to point to the style sheet. For example if you are viewing "http://www.somewhere.com/mypages/index.html" and you want to access the stylesheet shown in the example above, you will need to enter "http://www.somewhere.com/mypages/style/style.css" into the address bar.
When you are in the style sheet, do a search for font-family or font-face. That'll give you the fonts used.
This might not work though - the stylesheet classes might be in a folder the public can't access. Give it a shot though,