Viewport Dimensions – “Find your phone screen dimensions below in our handy list of viewport sizes by device.”
Viewport Emulator
6 Important Aspects of Well-Performing Mobile Product Page Breadcrumbs – “Yet our newest mobile benchmark reveals that, of mobile sites that even have breadcrumbs, 36% fail to include the full category hierarchy in the breadcrumbs on mobile product pages.”
Mobile Accessibility: How to Build Apps that Work for All Users
Mobile Web Best Practices 1.0
Mobile Web Application Best Practices
Mobile Screen Reader Testing