Extensively doing web development for the last 7 years. I guess what you need is the following.
1) Create a notifications area on the top part of your main page.
2) A JavaScript based interval will cause this area of the page automatically refreshed every 30 seconds.
3) The refresh of the area would be AJAX based and would grab the notifications from the DB, pop them up on the notifications area and delete from db.
4) In this way, usually it will be just one new notification outstanding to be displayed. However, if there are somehow more than one that arrive almost simultaneously, we would show all of them in the descending order of notification time i.e. latest on top.
5) I am confident that I will easily do it within one day.