[DanTzi]

there is a certain server that i wanna join but sometimes it writes he's offline and my friends can enter.

[Supercop]

nvm.

[lolcowtat]

This could be because your sa-mp client is a different version than the server. So if that server is .3d and your client is .3e you will not be able to connect. When you click the server and look at the bottom right corner it will tell you the version.