Onchange() not submitting values

Hi everyone,
I have a very weird issue here. I'm posting values using a dropdown box by using Onchange function in javascript. When I select any value in the dropdown only the first time the value is posted, but when I click the same dropdown and select some other value, it only calls the javascript function but does not submit the value. Please help me here..

My code is

<select name="classList" onchange="refresh();">
<option value="">--select--</option >
<?php
foreach($Class as $cls)
{
?>
<option value="<?php echo $cls['class'] ?>"<?php if($cls['class']==@$classList) echo "selected"; ?>>
<?php echo $cls['class'] ?></option>
<?php
}
?>
</select>

Code (markup):

And the javascript code is

 function refresh()
 {
  document.formName.action="";
  document.formName.submit();
 }

Code (markup):

 

This is a javascript problem, not PHP. You should show the entire HTML page or link to an online page we can try.