Web pages should specify their canonical URL (permalink)
I’ve been using del.icio.us to record items on ebay that I’m interested in. The problem is that each ebay page can have multiple URLs – none of which redirect to the canonical version. I can end up tagging the same listing twice if I happen to visit it with two different URLs – this is annoying. It wouldn’t be hard for them to either redirect to the canonical version or just add a
<link rel="bookmark" ... /> tag to the document. This way, I could ensure that I was always bookmarking the same version (even modifying the del.icio.us plugin if necessary).
This isn’t just a problem for ebay: lots of sites duplicate their content on multiple URLs (hello retailers). Maybe in the short term we could come up with some rules for turning any given URL on a specific site into its canonical representation. That sounds like a nice, useful, little service to me. Can someone build it for me please?