If you are experiencing trouble accessing a website, your first step would be to make sure the URL address is correct. Sometimes a site changes their URL addresses or can close their site all together. This could cause a hyperlink to not always be correct. If the address was typed in, check to see if you have typed the URL correctly. You can also try searching for a new URL via a web index.
In some cases you could be required to register and even pay a fee before gaining full access to a particular website. Additionally, if you are using a software to monitor or block access to particular resources that could be inappropriate for children, disable this application to access the site you wish to access.
Finally, the website that you are attempting to access could simply be overloaded or down. Wait a while and try again later.