Traffic to your website is very important, without any traffic your products or services would not be seen but it is very important to remember to check how well that traffic is converting.
If you have a high number of visitors but low sales / enquiries, then you need to stop and look in to why this is happening before pumping more money into your marketing. This can happen for several reasons but often it is that you are targeting the wrong audience or that your website is poorly designed / does not function as it should.
When working on marketing strategies, some companies think it is best to go for volume, so they will try and attract as many visitors as possible hoping that a percentage of them will then convert in to sales. This can work but often at a higher cost as you are marketing to some people that have no intention of ever buying a product or service from you. This is especially true of you are targeting them via Adwords or other Pay per Click programs where you are charged each time your ad is clicked on. This is why it is important to ensure your Pay per Click campaigns only target keywords / phrases of products or services you actually sell.