People can't open my forum

Hi I made this website http://pokemoncostarica.altervista.org and for some reason some people can't enter, any ideas why?

[saitfainder]

What you do mean exactly with "enter"? Is there someone who cannot read the posts? Or problems with registration? Please, give us some more detail.

Apparently when they try to click on the link the get a message that says "The connection has expired and the website is not available"

Other people get this message: "Protect your self, you are trying to go to this site http://pokemoncostarica.altervista.org/ the site is not secure, notify URL as not secure, continue or close window"

Why is this?

[saitfainder]

It looks like some anti-malware service has marked your site as malicious. Do you know which browser this users use and from which site are they coming from?