• An empty string ("")
• "hidden"
• "visible"

An element is visible when its style object's visibility property is either empty ("") or "visible". It is invisible when the property is "hidden".

When you initially place an element, its default visibility is an empty string (""). One would expect that setting the visibility property in the STYLE attribute, would switch the default value from "" to "visible":

<FORM>
<INPUT ID="button1" STYLE="position:relative; left:0; visibility:'visible';" 
  TYPE="button" VALUE="Show Visibility of Other Button" onclick="handleClick()">
<INPUT ID="button2" STYLE="position:relative; left:150; visibility:'visible';" 
  TYPE="button" VALUE="Show My Visibility" onclick="handleClick()">
</FORM>
<SCRIPT LANGUAGE="JavaScript">
<!--
function handleClick() {
  alert('visibility = "' + document.getElementById('button2').style.visibility + '"');
}
// -->
</SCRIPT>

Click the following buttons to verify that indeed the default visibility value is "visible" and not "". You'll find that this is the case in Internet Explorer only. Netscape 6, on the other hand, returns an empty string (""), so you cannot change the default visibility value in Netscape 6:

if (visibility != "hidden")...

You can also set visibility to "visible" in a JavaScript script. Needless to say, you have to do it before the first query of visibility.

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