Security warning what does this mean?

[Glenn]

So i am useing a pandigital 7" media tablet powered by android, win first set it up it say to set up a gmail acount well I did but I use my hotmail acount, so win I go to a web page like facebook,hotmail,yahoo and other site i get a box that shoes up and its says this, Security Warning
THERE ARE PROBLEMS WITH THE SECURITY CERTIFICATE FOR THIS SITE.
then there is a red box with a x in it,THE NAME OF THE SITE DOES NOT MATCH THE NAME ON THE CERTIFICATE. What does that mean and how do i fix it so it don't do that no more,

AND sent I have you on here how do I get it.to and apps it. Say i need to down load java but it.tell me it can what can I do.so i can do the app thing and to.be. abl to.use youtube