In a lotus form you can hide the fields enabling the check box “Hide paragraph from Web browser” in the window of the properties of the field but in this way the field is not generated as a hidden field, i.e. a html tag input with attribute type=”hidden” is not generated and you can’t access to its value from a browser, for example using javascript.
This is a different behavior from that one using a lotus client where you can still access to the hidden fields using lotusscript and formula language.