today is a fast day for all jews (at least the ones who are serious about thier religion), because today is the day in which both of our temples in jerusalem were burned down by the babylonians/romans. its a sign of mourning....
we also dont wear leather shoes, dont listen to music, dont play video games, dont sit on normal chairs until mid-day, and we sit in synagogue for a good 3-4 hours while we mourn for the temples and the disasters that have befallen the jewish people throughout history.