vBulletin Manual - Form Width

$stylevar[formwidth]

The form width StyleVar is used to set the width of all forms in vBulletin. Its primary function is to restrict the way that forms can stretch to fill all the available space in a window, which can cause form elements and their descriptions to stretch to levels at which the form becomes difficult to manage.

Here, at the default value of 640px, the form elements do not expand with the rest of the page, resulting in an easy-to-manage set of controls located in the center of the page:

With the value of $stylevar[formwidth] set to auto, the form elements stretch to fill the entire available space. This results in large empty gaps to the right of the form controls, with the controls themselves stuck to the left side of the window.

This StyleVar will accept any value that is a valid entry for CSS width. Examples of valid values include the following:

640px (640 pixels, fixed width)
75% (75% of available width)
auto (Expand to fill all available space)

Example of $stylevar[formwidth] in use:

<div style="width:$stylevar[formwidth]">
  <form method="index.php" method="post">
    <fieldset>
      <legend>My Form Example</legend>
      <input type="text" name="mytextfield" value="Hello" />
      This is my text field.
    </fieldset>
  </form>
</div>

Note:

This StyleVar is used as a CSS value. If you enter a width in pixels, you must add 'px' after the number of pixels desired, for example: '500px'.