Webdesign must communicate...
Clear navigation helps website visitors find the desired content quickly and easily. Don't let them browse through your entire site looking for it - because they won't.
The visual appearance of your website will communicate more than that. It will tell customers that you are serious about business. That you are willing to invest in customer relations. That you are different from your competitors. And ultimately, every person enjoys to do business in a pleasant environment. On the internet, that's your website.