Google recently introduced a way to tell their crawler which address variant you want indexed:
Now, you can simply add this
<link>tag to specify your preferred version:
<link rel="canonical" href="http://www.example.com/product.php?item=swedish-fish" />
This is very simple to set up with Tumblr. Go to the customization page,
and just before the </head>, add the following code:
{block:PermalinkPage}<link rel='canonical'
href='{Permalink}'>{/block:PermalinkPage}
This will automatically add the <link> element on pages for individual
entries. Index pages (i.e. pages that can have
pagination links) will just get a blank line.
