A website will not only give you credibility but it will also help to give the impression that your company is bigger and more successful than it may actually be. One of the great things about the internet is that the size of your company does not really matter. There is no reason that you can't get your site to rank in Google ahead of a large multinational competitor and funnel off some of their traffic. This is a big part of the reason that a website is even more important for a small business than a big one, it tends to level the playing field.