"And the Word was God." Here we have what are certainly the most widely discussed five words in the Bible. Is John here declaring that the Word is God the Father? A secondary, lesser god? Or One who possesses Deity in the same measure as the Father, but is also distinct from the Father? The word "LOGOS" is, again, preceded by the article. But the word "God" is not. While Greek possesses the definite article ("the"), it does not have an indefinite article ("a, an"). In Greek, the absence of the article usually signifies indefiniteness; however the grammar here makes that unlikely (see Grammatical Analysis, below). Definiteness is also a possibility, and indeed, many commentators and some grammarians see "God" here as a definite noun. There is a third option: Qualitative. Qualitative nouns occurs in sentences like John 1:1c throughout the NT. They do not signify definiteness ("the God"), nor indefiniteness ("a god"), but rather attribute all the qualities or attributes of the noun to the subject of the sentence. If "God" is qualitative, here, it means that all the attributes or qualities of God - the same God mentioned in the previous clause - belong to the Son.
http://www.forananswer.org/John/Jn1_1.htm