Forms
    form

    input
        text

    button type=submit

    form-action
        url: https://wa.toad.cz/~hurtapet/form.php

    input attributes
        name
        value

    form attributes
        method
        action

    label
        mention accessibility
        http://mobileinputtypes.com/

    input
        password
        number
        email

    radio
        name & value attributes
        checked

    checkbox
        multiple data with name="arrayname[]"

    select
        option
        multiple attribute

    textarea

    button
        type submit
        type reset

    validation
        required
        text
            maxlength
        number
            step
            min
            max

    fieldset
        legend

HTML validator
    https://validator.w3.org/

HTML Forms tutorial
    https://www.w3schools.com/html/html_forms.asp