Web Design in a Nutshell, 3rd Edition

Checkboxes can be used individually to transmit specific name/value coordinates to the server when checked. By default, a checkbox is not checked; to make it checked when the page loads, simply add the checked attribute to the corresponding input element. In XHTML, you must provide a value for every attribute, so the correct syntax is checked="checked".

When the box is checked, the corresponding value is transmitted with the form to the processing program on the server. The values for unchecked boxes are not sent.

If you assign a group of checkboxes the same name, they behave like a multiple-choice list in which the user can select more than one option for a given property, as shown in the following markup and in Figure 15-5.

    <p>Which of the following operating systems have you used?</p>
    <inputtype="checkbox" name="os" value="WinXP" /> Windows XP
    <input type="checkbox" name="os" value="Linux" checked="checked" /> Linux
    <input type="checkbox" name="os" value="OSX" checked="checked" /> Macintosh OSX
    <input type="checkbox" name="os" value="DOS" /> DOS

Figure 15-5. Multiple checkboxes in a group may be selected