Can not connect to website

recently, i have been able to get on it on and off. one day i can and the next day i cant, so idk what is going on with that

G'day - i am a new boy and have a similar problem.

just joined a motorhome site www.cmca.net.au and it worked perfectly till friday.
when i tried to connect with either firefox or int expl i get a message saying that "computer cannot communicate with 113.20.12.234 - windows diagnostics pinged and no response"
the site claim that they are on line but it is the only site that i cannot contact.
what is your best suggestion to a dill in this circumstance.
operating system windows vista

thanks for any guidance
peterseaford

well this time it worked for about a week and now it just stopped