Webmail sites doen't always work well with the iPad's Safari (and most third party browsers).
Best option (IMO) is to check with your email provider and see if they offer IMAP, Exchange, or POP server options; roughly in that order of preference. Then use that info to create an account on the iPad that you can use with the Mail app.
Second options. See if they have an app in the App Store.
Third. Ask if they have a mobile webmail site that you can go to instead. It would be best if it is optimized for tablets, but it should be usable if it's for smart phones.
Forth: Try some third party browsers that use remote servers. Your webmail problem is probably caused by the use of plug-ins not supported on the iPad. By running the session on a remote server you can bypass this. Suggestions are first, Opera Mini (because it's free), then Puffin or iSwifter.
Nothing much else to offer; though if you tell us who your email provider is other might have more specific suggestions.
