Trouble with Log In

I have a significant problem with logging in. As soon as I use wp-admin address it gives me an error message. I need to call the Hostgator everytime I need to update my site or otherwise login. Also, there is a problem with switching between the pages (going backward). It only works with the back arrow and not when I click on the pages. Going forward is fine. Please help.

The page I need help with: [log in to see the link]