HTML & XHTML: The Definitive Guide, 6th Edition

Creating Effective Forms

Properly done, a form can provide an effective user interface for your readers. With some server-side programming tricks, you can use forms to personalize the documents that you present to readers and thereby significantly increase the value of your pages on the Web.

Browser Constraints

Unlike other GUIs, browser displays are static. They have little or no capability for real-time data validation, for example, or for updating the values in a form based upon user input, giving users no help or guidance.^[*] Consequently, poorly designed web forms are difficult to fill out.

Make sure your forms assist users as much as possible. For example, adjust the size of text-input fields to give clues on acceptable input; five-character (or nine-character) zip codes, for instance. Use checkboxes, radio buttons, and selection lists whenever possible to narrow the list of choices the user must make.

Make sure you also adequately document your forms. Explain how to fill them out, supplying examples for each field. Provide appropriate hyperlinks to documentation that describes each field, if necessary.

When the form is submitted, make sure that the server-side application exhaustively validates the user's data. If an error is discovered, present the user with intelligent error messages and possible corrections. One of the most frustrating aspects of filling out forms is to have to start over from scratch whenever the server discovers an error. To alleviate this ugly redundancy ...