Could some on please check out this URL with Mozilla – http://smartplast.com/soon/ .
As you can see characters is displaying wrong :

I don’t understand where is problem, cause in all other browsers content is displaying right.
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Your server response HTTP header has encoding “windows-1251”, but the page itself is encoded in “UTF-8”.
Here is your header:
You can either set correct encoding in HTTP response header, or change encoding on the page.