with same IDs(per BLOCK), but in a time one only display:block the other two display:

[lse123]

May have in a web page HTML or HTML 5,... 3 DIV BLOCKS within each a <form> etc tags, with same IDs(per BLOCK), but in a time one only display:block the other two display:none (in a time)... can have this many IDs the same???

[traq]

I'm not completely sure what you are asking. If I understand correctly, NO, element id attributes must be unique. Only one element may have any given id; display/visibility doesn't matter.

If this is not what you are asking, please explain your question more clearly.

[lse123]

YES THAT MEAN... Well i have to use other Technics, so as IDs must be unique ALL either in display:none/block, like other client or server techniques... process one form from 3 different forms(one visible), like in a rent a car project having:
booking confirm page after a quote:
book without Register
book and Register
book and Social Register

correct?

[traq]

Will you only process one of the three forms?
Will you *ever* need to process more than one at the same time?

If they are exclusive (meaning you'll only ever process one of the three), then you can give the forms / form inputs the same name attributes (names can be the same; ids can not).

another option would be to simply have one form, and hide the inputs you don't need. for example (IIUC),

<form id="myform">
    <fieldset id="booking">
        <legend>Booking</legend>
        <p>This section is always visible.</p>
        <label>book: <input name="book"></label>
    </fieldset>
    <fieldset id="register">
        <legend>Register</legend>
        <p>This section is visible if the user is going to register,
            and hidden otherwise.</p>
        <label>register: <input name="register"></label>
    </fieldset>
    <fieldset id="social-register">
        <legend>Social register</legend>
        <p>This section is visible if the user is going to "social" register,
            and hidden otherwise.</p>
        <label>social: <input name="social"></label>
    </fieldset>
    <label>Submit the form: 
        <input type="submit" name="myform-submit" value="submit">
    </label>
</form>

[lse123]

yes since all results are a booking,... only one form used ever and processed....

if instead of "id" use "name" (PHP looks "name" attribute only in Post super global correct?) then in javascript use getElementByName("nameAttributeValue').value, correct?

[traq]

(PHP looks "name" attribute only in Post super global correct?)

correct

then in javascript use getElementByName("nameAttributeValue').value, correct?

you *could*, but since names are not unique, you'd need to figure out which one you want (since getElementsByName returns a list, not an individual item).

You can use ids and names together - use the id for javascript functionality, and use the name for processing the form in PHP.

[lse123]

is any way use keyword this with form.nameAttribute.value to get value?