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For SEO, it all depends on how you code it. If you want the landing page to have the SEO, you need to make sure the content is on that landing page, not a separate page being called. Lightboxes typically are coded all on the same page. Definitely pay attention to user experience stuff, like page speed and compatibility with different browsers. Page speed: customers expect your site to load in less than 2 seconds and will (on average) have an abandon rate of 40% if it takes 3 seconds to load your page. For compatibility, make sure to check out your analytics to see what devices/browsers the bulk of your customers are coming in on and test those.

Thanks for the tip Alan! SEOmoz is showing errors for all of these as it is causing duplicate content. We just launched a new site with a CMS and the search is a bit different than our old site. The site search has also inflated our site from roughly 400 pages to over 2500 in SEOmoz.

Having a good understanding of the site navigation and how internal page rank is passed is well worth it if you are doing a complete redesign.  Something I just came across may also be worth reading: The New Page Rank