For Mac OS users, there is a system setting that may not allow you to tab onto several types of elements in a web page. To change this setting:
Bell Schedule
First Hour 8:05-9:00
Breakfast 9:05-9:20
Second Hour 9:25-10:20
Third Hour 10:25-11:20
Fourth Hour 11:25-12:20
Lunch 12:25-12:50
Fifth Hour 12:55-1:50
Sixth Hour 1:55-2:50
Seventh Hour 2:55-3:50