Tumblr provides a version of your blog optimized for mobile devices. You can view that mobile version by adding /mobile to the end of your Tumblr address. Delivr (and Google Search/Transcoder) looks for the Tag to identify and redirect mobile visitors accordingly. That tag by default is not part of the Tumblr template so you will need to add it yourself. It’s easy and only takes a few seconds.
Instructions
Log into your Tumblr account.
Select “Customize” for the Tumblr blog you wish to modify.
Select “Theme”
Paste the following line of code within the Head tags of your template under the line of code that denotes the location of your RSS feed:
<link rel="alternate" media="handheld" href="{Permalink}/mobile" />