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:
I follow 1st lunch schedule
1st period – 7:55 – 8:48
2nd period – 8:53 – 9:53
3rd period – 9:58 – 10:51
4th period – 10:56 – 11:49
Lunch Break 11:49 – 12:14
5th period – 12:19 – 1:12
6th period – 1:17 – 2:10
7th period – 2:15 – 3:08