Spelling does not determine pronunciation. Period! English is a bit complicated language and most of us are mispronouncing words without realizing. Mispronounced words could also be embarrassing if you are speaking to a larger audience. Many people have turned it a habit to mispronounce words and they have no idea about the correct way in which a word is pronounced.
Here is a list of some of the most commonly mispronounced words even by most of the people whose native language is English.