For those who would prefer that visitors on iPhones see their actual website design, there is an option to disable the default mobile theme in tumblr. Go to Customize → Advanced → and uncheck “Use optimized layout on mobile devices”. Another option is to design and upload your own iPhone-optimized theme.

Up next: how to not install the WPtouch theme on your WordPress blog.

How to Disable the Default iPhone-Optimized Theme on a Tumblr Website