Those sound like browser based messages alerting you to the fact that there is, for example, flash content on the page and you do not have the Flash player plugin or it is outdated (Flash has been a prime target for exploitation of late). Just because you bought your laptop 3 days ago doesn't mean the software is current. The image used to load the software on that computer might be several months old.
So, short of screenshots or something showing the specific messages you're getting, it's difficult to say whether or not they're legitimate or not.
While on a website I am looking at, an ad will pop up and cover what I am reading - very annoying. It does not even have the exit button (x) , won't go away, if I got lucky to get out of it another one will show up - just won't go away.
An example is an ad telling me to update the flash player or I am missing. a plug-in. And reminds me also that I can uninstall later if I need to. (And my laptop is brand new only 3 days old). How do I get rid of these stubborn ads?