One way to translate a web page is through localization i.e. by putting all page text para-by-para into resource (.RESX) files of English, Spanish, German, etc. after respective translations.
the other faster way is by using Google Translate API, see the link- http://code.google.com/apis/ajaxlanguage/
You can find a developer guide of Google Translate API at http://code.google.com/apis/ajaxlanguage/documentation/
and Example project at http://code.google.com/apis/ajaxlanguage/documentation/#Examples
But, the most efficient way is still the first one. Google and other translation APIs are not very efficient in giving gramatically correct translated text.
Try it and see...