A this site message refers to just a singular site. Are you able to access any sites at all? Also, have you tried testing the internet connection, to see what speed it says you are getting? You may want to consider trying another browser, to see if IE is the problem.
I would also try connecting with a different device and see if it can connect.
Should it keep telling you that there is no access to any site (not just one) and happen on more than one browser, plus not let other devices as well, then I would contact your ISP and find out if there is a problem.