Handling Search engines with 404 and redirection in product list

I have quick question for you all :)

Let's say we have an eshop with URL's like type-of-product/name. Now, We have redesigned and reprogrammed ou开发者_运维知识库r website, so now we need to redirect URL's from old ones  products-name.htm to new ones. That is not problem

The question is – how to handle products, that are not available anymore – so they don't have 'new URLs'? Basically, we have three options:

1. 404 them all
2. redirect them to homepage
3. create one page "product is not available anymore" and redirect all old products to it.

Which is in your opinion best a., for users and b., for search engines?

Thank you

1) Would be the best option SEO-wise. Product not available - no point in keeping its old page in the search engine index.

2) If you make a redirect, search engines will see multiple links ultimately linking to the home page. may confuse them PR-wise.

3) Better make a 404 with the text message "product is not available anymore". User-friendly and search-engine friendly.

P.S. 404 is okay if the product page only contains the product description. If there is some useful content like user comments which do generate some [valuable] traffic, I'd probably go the extra mile of creating new links for old products.

Since the products (and therefore the pages) did exist but don't any more, you should use a 410 Gone response instead of a 404 Not Found. Combine this with a document that explains that the product is no longer available and suggests possible alternatives.