У вашего броузера проблема в совместимости с HTML5
1. Go to "(your drive)\Steam\steamapps\common\dota 2 beta\dota\cfg"
2. Open "video.txt" file
3. Look for
setting.defaultres
and
setting.defaultresheight
4. Set it to your DEFAULT screen resolution
Ex. "setting.defaultres" "1920"
"setting.defaultresheight" "1080"
5. Go to "(your drive)\Steam\steamapps\common\dota 2 beta\game\dota\cfg"
6. Open "video.txt"
7. Look for
setting.defaultres
and
setting.defaultresheight
8. Set it to your DESIRED screen resolution
Ex. "setting.defaultres" "1920"
"setting.defaultresheight" "1080"
9. Look for setting.fullscreen_min_on_focus_loss and set it to 0
Ex. "setting.fullscreen_min_on_focus_loss" "0"
10. Open steam and open Dota 2. Problem fixed!