Two dots on the "i" instead of one? [duplicate]

Possible Duplicate:
“Whereäs” as an alternative spelling of “whereas”
Is it spelt “naïve” or “naive”?

Someone I talked to used two dots in this word:

Naïvely

I thought that it's my screen having dirt on it, but the dots in fact are part of the glyph. Can someone explain that?

The origin of "naive" is the French word "naïve". (Notice that the French "naïve" is italicized)

As a French word, it is spelled naïve or naïf. (French adjectives have grammatical gender; naïf is used with masculine nouns while naive is used with feminine nouns.) The two dots above the "i" are called diaeresis. As an unitalicized English word, "naive" is now the more usual spelling, although "naïve" is unidiomatic rather than incorrect.

For more, look up this.