I’m about to add a product filter to me site, such that a user can come to a category and use the specification filter to bring up the products they want. In the different ways I could achieve this I’m also considering SEO implications.
First off, I would like, by default, for the solution to be ajax-based, for speed/ease for the customer. I could implement use of URL fragments and suchlike for bookmarking & historying (another question - when using this kind of dynamic product filtering would you, as as user, expect the back button to take you back to your previous filter selection, or not?). If I were to do all the action on the same URL I guess I’d need to be wary of Google finding the ‘new’ content and diluting/affecting the ranking/relevance for the main URL. Eg if it’s a category /teddy_bears which normally shows subcategories of teddy bears, but the filter causes it to show a list of products, wouldn’t Google not like that, even with a canonical tag (the content differing too much)?
Another option is that the form submits to a page, with a different URL (eg /teddy_bears?type=fluffy&colour=brown). How about if that’s the default action of the form (for non-javascript users, and I guess for search engines), but my javascript prevents a page load and just loads the new content in a section on the current page. Would The engines find that?
Any thoughts?
I don’t see a problem with the solution you’ve suggested - Google has to accept that sites can offer Ajax and accessible versions and so it may sometimes see things in a different way to most people, I don’t believe that would be marked down as cloaking. In terms of the canonical tag, evidence from the field seems to be that Google doesn’t police the “content must be very similar” to carefully, as there have been instances of entire sites or sections that Google has ignored because they’ve had the canonical set to the home page.
PS - please don’t “bump” your own posts. It’s rude, and it may be counter-productive, because they will no longer show up on the “unanswered threads” option, meaning people who use that will assume it’s been answered so won’t bother looking at it.
Thanks for your response and I note your comments.
DO you think the use of a URL /teddy_bears?foo=bar&cat=dog&stuff=etc would at all detract from an already well ranking page with URL /teddy_bears ?
I think any page that has &cat=dog in its parameters has bigger things to worry about 
Partly it depends on what people are searching for and how specific your categorisation goes. If most people are just searching for “teddy bears” and your site is ranking well for that then you probably don’t want Google to spend too much time indexing all the different variants separately, you just need to promote the one page. But if most of your target traffic is going to come from searches like “fluffy brown teddy bears with one eye from Romania” then you want Google to really go to town with the detail, and give people the exact results they’re searching for rather than just dumping them at a generic “teddy bear” page and making them do all the work.