Javascript weird prblem

Yii 1.1 General Discussion
1

Why can it get into the function but cannot getElementbyID??


<script language="javascript" type="text/javascript">


    function displayField(){

        alert("T: "+document.getElementByID("test").style.visibility);

    }


</script>


<h2 style="text-decoration: underline;text-align: center">Customized Report Generator</h2>

<?php

include_once '_customReprotVariables.php';


echo '<div id="test" style="visibility:visible;display:block">TEST</div>';

...

echo CHtml::button('Personal Information', array('onclick' => 'displayField()'));
2 

'onclick' => 'js:displayField()'

its easier to use jquery




alert("T: "+$("test").css('visibility'));

to register the jquery use




Yii::app()->clientScript->registerCoreScript('jquery');