Twitter’s Bootstrap – create a form with 2 columns

Wrap the form tag around your span divs. This is working for me, but you might need to tweak things a bit:

<div class="row">
  <form class="form-horizontal">
    <div class="span6">
      <fieldset>
      <legend>Legend text</legend>
      <div class="control-group">
        <label class="control-label" for="input01">Text input</label>
        <div class="controls">
          <input type="text" class="input-xlarge" id="input01">
          <p class="help-block">Supporting help text</p>
        </div>
      </div>
      </fieldset>
    </div>
    <div class="span6">
      <fieldset>
        <legend>Legend text</legend>
        <div class="control-group">
          <label class="control-label" for="input01">Text input</label>
          <div class="controls">
            <input type="text" class="input-xlarge" id="input01">
            <p class="help-block">Supporting help text</p>
          </div>
        </div>
      </fieldset>
    </div>
  </form>
</div>