case test jquery.validate

HTML

<script src="http://ajax.aspnetcdn.com/ajax/jquery.validate/1.8.1/jquery.validate.min.js"></script>
<form><label>Select Tank:</label>
<select class="text2" name="tank" id="mySelect">
          <option value="0" selected="selected">Select your tank</option>
          <option value="4"> Tank#1 </option>
          <option value="9"> Tank#2 </option>
          <option value="21"> Tank#3 </option>
          <option value="34"> Tank#4 </option>
      </select>
<input type="button" id="btncheck" value="Submit"/>
</form>

JavaScript

$('#btncheck').click(function(){
     if ($("#mySelect ")[0].selectedIndex <= 0) {
		 alert("Please select a tank from the menu!");
				return false;
				}
    else {
        return true;
		form.submit(); 
	}
});