Since I had started to use Firefox, I found that it is faster than Internet Explorer, but I cannot go in some games' page. Why? Is it because the sites are not updated ?

Most of the webpage problem is caused because the web designer had used some code that is not standard - especially IE only code,
you can contact the web's owner and letting them know that.

if you want to know more about "why this page cannot display accuracy", maybe you can tell us which page you faced the trouble, that many friends can help you to find out.