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This is the only case study I have seen about alt tags http://www.hobo-web.co.uk/how-many-words-in-alt-text-for-google-yahoo-bing/ 16 words of 7 + 8 characters each

Now THAT's why I wish I could afford an SEO consultant!

Anthony's definitely got the basics covered. How to handle any particular situation can get pretty tricky. I wrote a post about it, and that post got very long very fast: http://www.seomoz.org/blog/duplicate-content-in-a-post-panda-world I took a quick look at your campaign (I have Staff access), and it seems your login page is carrying an event ID - so every event is creating a different URL, but they all land on one page. That could spin out 100s of duplicates on Google, and that login page has little or no search value. A canonical tag would definitely be a good bet here. You may have other issues going on, but clean up one at a time - getting that number down can definitely be beneficial and help boost your ranking power.

Thanks Mat!