У вашего броузера проблема в совместимости с HTML5
Responsive Columns Layout from floating to flexbox:
- 3 Columns (large and medium screens)
- 1 Column (Extra small screens)
- Change div's order in the extra small screens.
Part (1):
https://www.youtube.com/watch?v=IVZTjmZI0CM
Part(2):
https://www.youtube.com/watch?v=cf414A-F20I
Part(3):
https://www.youtube.com/watch?v=XrzMTwpC1tk
Part(4):
https://www.youtube.com/watch?v=WFiXQriMjQc
Part(5):
https://www.youtube.com/watch?v=S4XkQOKOBwo
Part(6):
https://www.youtube.com/watch?v=-j0752ioTOY
Part(7):
https://www.youtube.com/watch?v=lsS3-AkZiaU
Part(8):
https://www.youtube.com/watch?v=-4Ufyg-KriE
Part(9):
https://www.youtube.com/watch?v=l-d2ONaY3BE
Part (10):
https://www.youtube.com/watch?v=2Yh2YaLEvy0
Part(11):
https://www.youtube.com/watch?v=Ch3MoEGMdIw
More:
https://annsaid.com/