The silent 't' was the prescribed pronunciation back a generation or two, but now many pronounce the 't'. (I have even been corrected by people, when I don't pronounce the 't', which is what I learned in school. As others have said, both pronunciations are considered correct, at least in US English.

There are other words, where English silly spelling system has influenced pronunciation. When Middle English speakers borrowed parfit from the Normans, it was pretty much pronounced as spelled. Then the spelling changed to reflect its Latin etymology, perfect, but still pronounced parfit. Before you knew it, it was being pronounced /'pErfEkt/.

Even Spanish has some differences in pronunciation (that have changed over the years and are partially regional, url=v]link[/url]). (Although its orthography it much better than English.)

Ceci n'est pas un seing.