There are many reasons for a domain to be blocked or not blocked. One of the reasons could be because of the type of category the domain is tagged under. Another could be the domain is showing malicious activity therefore is being blocked for security reasons. Why is this site being blocked?
CAUSE. Java has further enhanced security to make the user system less vulnerable to external exploits. Starting with Java 7 Update 51, Java does not allow users to run applications that are not signed (unsigned), self-signed (not signed by trusted authority) or that are missing permission attributes.