Able To Hide <div> With Javascript In Firefox But Not IE?

I have a php page with a drop down list, and the default selected
option is "Select a location" (without quotes).
Using the drop down initiates a database query. One of (3) things
should happen:

1. If an option is selected for which results are available, they
should be displayed on the same page beneath the drop down list in a
table.

2. If an option is selected for which results are NOT available, a
message should be displayed informing the visitor that there were no
results for that query.

3. If the default selected option has not yet been changed (ie: when
the page first loads), no message should display.

#1 and #2 work, but the message described in #2 is still displayed when
the page first loads before the default selected option is changed (#3)
but in Internet Explorer only. Firefox displays the page correctly
under all three conditions.

The message that I want hidden on page load is wrapped in a div named
"infobox" and I'm using the following script to hide it which is at the
bottom of the page:

<script language="javascript" type="text/javascript">
function ClearDiv()
{
if
(document.form2.name.options[document.form2.name.selectedIndex].value=="Select
a location")
{
document.getElementById("infobox").style.display =
"none";
}
}

ClearDiv();
</script>

I've also included the php code that writes out the message and the
table below....