I made a minecraft and and now the connection thing is crossed out and it says in red 1.7.5?

Ok so i made a server on my mac about a week ago, and i could connect and play on it. But now when i go to connect it shows the connection bars crossed out and in red above them it says 1.7.5. Anything would be helpful because i don't know what to do.

It means that your server is out of date for the current patch. You need to update the Minecraft_Server.exe or whatever it's called.