It's 2007.
Like it or not, we're living in the digital age. If you don't have even a basic website, it raises some eyebrows about your client's credibility.
It automatically expands every other advertising dollar you spend tenfold.
I've tried cramming information and branding and value-drivers and the kitchen sink into a 2 column newspaper ad. Or a lawn sign. Or a billboard people will be passing at 70 mph. You can't do it. But with one short, memorable string of characters-your client's web address-you can point everyone that comes across your client's ad, sign, or radio spot to all the information you want them to have.