Multiple forms in JavaScript

Hi,

I am new to Web Development. Currently I am working on a webpage that has multiple forms (start date calendar, end date calendar, checkboxes, etc) and I need to validate the fields to make sure that the user has entered all of the required fields. The only way that I have seen to do form validation involves putting a form around almost all of the code. I have been told that you cannot nest forms. Can anyone offer me any suggestions on how to tackle such a taske? I would appreciate any assistance that you could give me. Thanks in advance!!