If your website has a purpose (in other words its not just a family blog where your nearest and dearest can keep up to date with your happenings) then there is something specific you want your visitors to do - buy something, sign up for something, etc.
Far too many webmasters become so familiar with their sites that it is "obvious" to them what a visitor should want to do - to the visitor who has just stumbled across a page however it may not be that clear at all.
I've seen product pages on Ecommerce stores where it is actually difficult to find the 'Buy Now' button making it easy to conclude the page is just general information about the product.
I've seen blogs where the 'newsletter signup' needs to be tracked down - it can be two or three clicks away and they are not always obvious clicks.
I've seen bricks and mortar local businesses put their contact information (such as their map and address!) in the strangest of places.
Making it absolutely clear to your visitors what it is you want them to do is known as giving them a clear 'Call to Action' - known as CTA for short.
On an Ecommerce site this means a prominent 'Buy Now' or 'Add to Cart' button close to the price and preferably above the fold. On other sites it could be a 'Try our Free Trial' link which appears regularly within the content or (as happens with this website) scrolls with the page and so is always in view.
From an SEO perspective the question to ask yourself is this: "Would a person who arrives on any page of my website know what it is I'd like them to do?".
Call to Actions are often the subject of A B Testing. For example if the purpose of your website is to generate leads:
Although these might sound like very small tinkerings they can have substantial effects. If your conversion rate rises from 1 person in every 100 to 2 people in every 100 that's a 100% increase!!!
Call to Actions which work keep visitors on your website longer which:
I'm Tim Hill, a Search Engine Optimization and Online Marketing specialist. I created this site to help others understand that SEO is not a mysterious black art!.
If your a newbie try the Getting Started in SEO page, otherwise feel free to dig around and learn more.