Maybe you don't

It depends on what kind of business you are running... 

If you have a small business spending most of your time working on site and do not need any more customers, then you're in a good place and probably don't need to invest in a website. 

Similarly if you have a situational business that relies on passing trade, a website to advertise your services may not be necessary.

Or if your customers are more likely to pick up the Yellow Pages than to search on Google then you may better off in the short term to invest in a bigger, bolder Yellow Pages advert (we can help with that too!). However see this article on Digital Britain, as this is soon to change. 

Probably you do

A website is a good idea if any of the following is applies to your business: You...

1. know your customers are likely to use the Internet.
2. want to grow and market your business.
3. want to attract customers from more locations.
4. want to sell products online.
5. believe you could save costs by providing information and services to your existing customers or supply chain.