If you want to setup same viewport (e.g. 400) for iphone and android is hard.
- width=device-width doesn't work, since each device has different default width.
default width of iPhone/6/6+ are 320, 375 and 414
default width of android are 320, 360 and 400
- width=400 or width=360 doesn't work in iPhone
- width=320, initial-scale=0.8 is not a good solution. iPhone is work, but android doesn't work except user-scalable=1