If you have a better browser, you can try this (like in this thread):

<select required>
  <option value=""></option>
  <option value="basic">Basic</option>
  <option value="plus">Plus</option>
  <option value="premium">Premium</option>
</select>

, but still you should use JavaScript because not a lot of people have browsers that support HTML5 required attribute. It's not supported by IE and Safari.

check this: http://www.w3.org/TR/html-markup/select.html

global attributes Any attributes permitted globally.

1. name = string

   The name part of the name/value pair associated with this element for the purposes of form submission.

2. disabled = "disabled" or "" (empty string) or empty

   Specifies that the element represents a disabled control.

3. form = ID reference NEW

   The value of the id attribute on the form with which to associate the element.

4. size = positive integer

   The number of options to show to the user.

5. multiple = "multiple" or "" (empty string) or empty

   If present, indicates that its select element represents a control for selecting zero or more options from a list of options. If not present, indicates that its select element represents a control for selecting a single option from a list of options.

6. autofocus = "autofocus" or "" (empty string) or empty

   Specifies that the element represents a control to which a UA is meant to give focus as soon as the document is loaded.

7. required = "required" or "" (empty string) or empty

   Specifies that the element is a required part of form submission.

so you require a required = "required" attribute to your <select>