The general rule is,never work out the same muscle group 2 days in a row.You usually want to leave a gap in between to let the muscles recover.
But,when it comes to abs,it's a different story.Abs recover faster than any other muscles in the body.If you do abs today,they will have recovered and be ready to work them the next day.So you can basically work them out everyday with no worries.
The soreness doesn't mean that the muscles are damaged.When you work a muscle group harder than what it's used to,water retention occurs,and this adds pressure on the nerve endings.After the water retention is gone,you won't feel soreness anymore if you consistently work the same muscle group. Alot of people think its because of lactic acid buildup which is totally wrong,it has notihng to do with lactic acid.