Why do my frames keep looking like they're "selected" ?

Sorry I'm really new to flash and I'm just learning it!!!

Sometimes when I go back to a frame I notice my lines look like they do when they're selected (???idk). Like it's dotted and light gray and around all the lines (pencil tool). When I play my frames back, they dotted gray makes everything really bulky looking. I need to go through each of the affected frames individually and mouse over it to get rid of it? I don't understand what this is but it's really annoying?