Bad Webfont Quality

I'm not quite sure if I can ask this question here, so if it doesn't just delete it.

I'm having a strange problem with webfonts..

While I encoded my site on firefox, I pressed F5 and then I saw the webfonts very bad. I tried to enter to the site via Google Chrome and I saw it well. but after a while Google Chrome started to show me bad quality too!

Image for example (on firefox + chrome): [Bad Webfont Quality][1]

So now when I enter to the site via Internet Explorer I see the font fine..

[Image for example (IE):][2]

as you can see, there's a big difference between them..

I use Windows 8 and the font I use is called "Roboto" from Google Fonts

Any Help?