div shows queried data, but then page reloads.

[turpentyne]

I have a catch-22. I built a simple page that pulls several items from the database, and lists them. Now I need to add a "pop-up" div that shows detailed information for an item, if they click on it. I have it working right now, but instead of reloading the page with the div showing and done, it somehow shows the div with the information from the database, then reloads the page without it showing.

 

I'm not quite sure how I can send the info to the javascript

 

 

<!-- the simple javascript at top of page -->
<script type="text/javascript">
function showdiv(id){
document.getElementById(id).style.display = "block";
}
</script>

<?php 

/* other code that pulls the initial information here */

/* including... this, where the _get id is passed, and includes the call to the javascript function that shows */
$ExpandImageTemplate = <<<OutHTML
<div style='width:70px;padding:15px 15px 5px 10px;float:left;width:150px; min-height:140px;overflow:auto;'> %4\$s <br>
<a class'hide' href="http://www.mcmillanusa.com/mcmillan-rifles-alias-accessories.php?id=%4\$s" target="_self" onclick="showdiv('pop-div');" ><img src="%3\$s" style="border: solid 0px #000000;max-width:150px;"></a></div>
OutHTML;

/* taking some query results to create the above - irrelevant to the question */
$Output .= sprintf ($ExpandImageTemplate, htmlspecialchars ($row['comp_cat_name']),htmlspecialchars ($row['folder_path']),htmlspecialchars ($row['image_filepath']),htmlspecialchars ($row['component_name']));


?>
<!-- then, further down on the page, here's the code that I was trying to write to create the pop-up div I couldn't put it above because it's screwing up a database query for other unrelated stuff -->
<?php 
/* still need to add security for the _get statement, but on page reload, this variable $which_one is set  */

$which_one = ($_GET["id"]); 

$result = mysql_query("SELECT *
FROM `tbl_components`
WHERE `component_name` = '$which_one'")
or die(mysql_error());  

$row = mysql_fetch_array( $result );

echo "<center><div id=\"pop-div\" style=\"display:none;width:700px;z-index:99;height:0px;overflow:visible;color:#000;\"><p style=\"position:relative;left:-48px;background-image: url('../../images/alias/alias-pop-bg.png');width:605px;height:400px;padding:10px;\"><b><span style=\"width:200px;\"><font style=\"color:#fff;\">".$row['component_name']."</font></b><br><br>";
echo "<font style=\"color:#fff;\">".$row['component_description']."</font>>/span><br><br>";
echo "<img src='".$row['image_filepath']."'><br></p></div></center></div>";

?>