Aruthur, it is not possible to hack an iPad via websites. Apple's iOS operating system is very secure and unless you jailbreak it, it is not possible to hack it via websites. Someone need to have physical access to your iPad to hack it, but only by jailbreaking it.
If there is no Cydia, then it is not jailbroken.
As long as it is not jailbroken, you don't have to worry. Also, I'd recommeend to update iOS 8. You can update it from Settings > General > Software Update.
Or you can update it from iTunes on your computer. Get iTunes from here : http://www.apple.com/itunes/downloate
Upgrading to latest version of iOS will make your iPad invulnerable to security threats.
Not sure what happened when you visited that website and provided the password. Believe me, your iPad is safe since it is not jailbroken. Now one can hack your iPad using websites. The websites can't access the system files of your iPad, so they can't infect it with spyware or viruses.
Again, update your iPad to latest iOS versions and you will be safe. Now, to make sure there is nothing on your iPad you can reset some settings. Goto Settings > General > Reset and tap Reset All Settings. Then goto Settings > Safari and tap Clear History, Cookies etc
If you have any questions or would like any additional information, please don't hesitate to ask.