Why do I have such drastic differences in my ratings?

[EcommerceSite]

I work for an e-commerce site that has quite a few categories. Some of these categories rank really well and other don't rank at all. What causes such a drastic difference?

I understand that there are a lot of factors in ranking, so I am not asking why am I ranked #1 in some keywords and #2 in others. What I am trying to figure out is why I rank #1 in some keywords and don't rank in the first ten pages in another. The pages and optimization are the same. Why wouldn't it rank at all?

[OlegKorneitchouk]

• keyword difficulty
• external backlinks to specific categories/products
• internal link structure to specific categories/structures
• content (product descriptions, category descriptions) on the related categories

[EcommerceSite]

The keywords are low competition.

The external backlinks are the same.

The internal structure is the same. site/category/subcategory

The pages are all done in .net and pulled from the database. There are a few sentences but it is mostly a list of products like http://www.ebay.com/bhp/used-bakery-equipment

This isn't just one category or I would say it is out of the ordinary. We have about 300 total categories. about 200 rank great, and 100 don't.

[OlegKorneitchouk]

No patterns? e.g. ones that rank worse are linked lower/later in the category list

Internal structure i meant like are some categories interlinked better (from blog posts, featured sections, etc)

Is the text unique on all categories?

[EcommerceSite]

I just went through the top 150 keywords that brought people to our site to before we switched to our new structure to see if I could find a pattern and it is all random. My first thought was that something was moved farther down the subcategory list but there was no correlation.

Many of these pages have almost none or no links. We have links coming to the site but not every category page. We have some category pages with zero external links rank #1 for our keyword.

The text is unique. They are category pages so there will be some similarities, but the content and items listed are different.