Ok the problem you are experiencing is a DNS server issue.
There are big mainframe computers that are located at the main traffik hubs that all they do is translate the domain names (eg: google.com) into numbers (188.8.131.52) to pass the packets to the appropriate web sites or ISP's.
Occasionally these go down just like any other system and then they have to be reloaded from the start. Fortunatly this doesnt happen too often.
What I suggest is that the next time this happens is that you contact your ISP and let them know. They can in turn notify the main frame center that there is an issue with their DNS servers.
There are a couple proceedures that your ISP will walk you through in order to ensure that it is not your computer that is causing this. They have the capability to observe a packet being sent to the web site from your computer and see where it goes, or doesn't go.
If you would like to see how a packet is routed to the web site you send your email to just type in the same thing as above but leave off everything after the / eg: "tracert mail.yahoo.com" It was the rest of the command (the syntax [how a command is written]) that was screwing things up. Sorry about that. My bad.
You can also read about the tracert command by typing "tracert ?" after the command prompt.
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