Transitioning URL style

What's the best strategy?

[scooch]

Currently my URL looks like this:

www.domain.com/widgets?style=blue
www.domain.com/widgets?style=yellow
www.domain.com/widgets?style=red

"widgets" and "blue", "yellow", "red" are all important keywords.

To improve search engine placement, I'm planning to transition to a different URL model:

www.domain.com/widgets/blue
www.domain.com/widgets/red
www.domain.com/widgets/yellow

(actually, I have a question about how I should best format the URL, but I'll do that in another thread.)

When I do this, most of the pages on my site will change to the new model and search engine traffic will still go to the old model.

What's the best strategy for the transition so as not to jeopardize spidering and SERPS?

1. Keep pages on the old model until the search engines pick up the new one? (could this be seen as duplicate content?) or
2. Server-side redirect the old pages to the new one, or
3. Something else?

Thanks for your advice.

[seindal]

Make sure each old address does a redirect to the corresponding new address. The search engines will follow the redirect just as the browsers do.

The search engines will gradually update there indexes with the new pages and phase the old pages out, as they all redirect. In a month or two the whole transition should be over.

René.

[scooch]

Thanks. Here's what I did:

1. Created a new page that takes the following format:
www.mydomain.com/new_widgets.php?style=red

2. Set up a mod_rewrite that looks like this:

www.mydomain.com/kw1_kw2_red_widgets.html
which goes to that new page:
www.mydomain.com/new_page.php?style=red

3. Changed the original page, /widgets.php?style=red
to server-side-redirect to
/kw1_kw2_red_widgets.html

kw1 and kw2 are just some common keywords that I threw in there for good measure.

I did the mod_rewrite thing instead of /widgets/red as the PR of the page dropped a point because of the apparent extra directory level. Don't know if that really matters, but I feel better :)