Certain combination of letters create a symbol

Hi there,
I have a weird problem and I encounter it since some time now. It only occurs when I activate Themes that come with custom fonts.

I realize it happens when the letter combination is “ft”.

At this site you can see a test page with my actual theme:
http://05erfan.info/blog/ft-testing/

And here you can see what happens when I try to use RubberSoul (Version: 1.4.0).

I don’t know if this is only a font phenomenon or something else.
Maybe someone can help me?

And it just happens until the h3 Heading.

Edit: It seems that this is a problem caused by the plugin WP Google Fonts. I will get in contact with the developer of that plugin.