Thank you for your inquiry.
Were you able to access these sites in your laptop in the past? Are you getting any error message when you try to access youtube, yahoo and mygov?
First, try to clear the history of your browser. This usually does the magic. If this doesn't work, connect your laptop to the modem using a cable. If you can access the sites without a problem on a wired setup, access the setup page of the modem and try to change the wireless channel. However, if the websites won't still load on wired connection, check your security software and make sure that the sites are not blocked. You may also try to connect another wireless device in your home wifi and observe if the same thing happens when you try to access the websites.