One step in SEO efforts that is often overlooked is that of comparing what you think your web page looks like against what the search engines see. There are several scenarios where this is crucial to the success of your organic search growth.
http://www.5vote.com is a website that shows off photos and allows people to vote on the ones they like the most. Here is a screen image of what it looks like to a standard user:
However the Google Search engine (and others) interpret the website and see it as the following:
Actually, if you wanted to get technical, the search engine actually does not interpret the colors and spacing... but the above visual example is what I wanted to convey.
How do you fix this then? Well there are a couple routes and none of them are easy.
Another way around this error is to have a secondary page that displays the information needed for search engines. Then when users land on this page you can redirect them to where they should be going. I actually don't like (and have stopped recommending this method) because at times the search engines will interpret it as a bait and switch method. I.E. you are having Google indexing one thing and displaying another.
Case 2: If you site has a lot of it's primary content behind a login or members only section.
Another common scenario is when you have specialized content that may be hidden behind a members only area. The plain and unfortunate truth is that the googlebots do not see this content and cannot index it.
One of the best ways to get around this is to offer a preview of each piece of content. If your site has specialized articles then you may offer the first paragraph or two in an open and free format. Google really only needs the first ~300 words or so to determine the prominent keywords. If you do choose this route, determine what the keywords are that you are targeting for each article. Then ensure that you play those up on your preview pages. Include the keywords in the title, description, image assets, H1 tags and other spots on your page.