Search Engine Optimisation (SEO): If you're not there, they can't click.

The starting point for any serious online marketing programme is your site's 'natural' visibility — its position in the search engine results pages ("SERPs"). This is a supremely powerful component of the online marketer's toolkit… eye-tracking studies show that the top three positions in the SERPs have 100% visibility (every single searcher sees them), whereas top ad positions seldom achieve better than 50% visibility.

And of course, unlike sponsored ad clicks, natural search clicks are free — and you can't beat the ROI on free. What's more, a naturally high-ranking website significantly boosts the return on investment for any budget you do put into Pay-Per-Click ("PPC") marketing.