The blue dots are "breadcrumbs" which are left if you have tracking turned on. In the device you can set how often a point is set. The can be deleted from the the left menu. Again I would go through the Garmin Support site and watch a few videos or read so you can understand the device and web interface better. When you click one of the dots it does give you the pop-up. That is really meant for people to contact you. It also shows the lat/long of the interval point as well.ok thanks...
If you look at the blue highlighted track summary on the left if I click the trash can and confirm I want to delete it, it will disappear from the map. I am no Garmin expert though.