HTML and CSS Certification Practice Test

The attribute 'disabled' in a form input serves to make the input unmodifiable, meaning that users cannot interact with it; they cannot enter or change any information in that input field. When an input has the 'disabled' attribute, it is also excluded from form submission. This means that any data entered into a disabled input will not be sent to the server when the form is submitted. This attribute is particularly useful for preventing user input in situations where the field should not be altered, such as when it is meant to display information that is read-only or when a certain condition is not met for the input to be active.

In contrast, making an input invisible or editable does not accurately describe what 'disabled' does. Highlighting the input field also does not relate to the functionality provided by the 'disabled' attribute. The primary purpose of 'disabled' is to ensure that certain fields are not modifiable and aren't included in the data payload when the form is submitted.