I have a site about plants, The Seed Site. My Pagerank went down from 5 to 4 a while ago, and nothing changed when I added 100 new plants. I keep getting these SEO emails, and I'm wondering if Google is counting some of my pages as duplicate, so not including much of my information.
There is a lot of duplicate HTML code on many of my pages, as they include the same things about different plants or parts of plants. For example, I have a page identifying seeds, which lists them in alphabetical order, which is almost the same as the one about seedlings, or seedpods. Anyone looking at the actual page could see they're different, but a computer looking at code, especially if it's only a bit of code, might see them as all the same.
Individual photos of different parts of plants are also on other pages, in different contexts. There is always a heading on each page, indicating what is on the page, but I've read that Google doesn't always look at this.
I don't want to add ALT to all the pictures, as that would result in a lot more code, and a lot of my visitors come from countries where internet connection is probably slow, but obviously I want Google to include all my pages.
I did look on Google help forums, and I wonder if I need to make a Sitemap (which I don't at present know how to do).
Can someone tell me (a) whether it is probable that Google is counting some of my pages as duplicates, and (b) if they are, how can I get round that? If it comes to a choice, I'd rather please my visitors than Google.