error is:- content is not a function. why the function is not called

<?php
	$db_host="localhost";
		$db_name="fck";
		$username="root";
		$password="";
		$db_con=mysql_connect($db_host,$username,$password) or die("connection not build".mysql_error());
		$db=mysql_select_db($db_name) or die("database not build".mysql_error());
?>
<script language="javascript" type="text/javascript">
function createObject() {
	var request_type;
	var browser = navigator.appName;
	if(browser == "Microsoft Internet Explorer"){
		request_type = new ActiveXObject("Microsoft.XMLHTTP");
	} else{
		request_type = new XMLHttpRequest();
	}
	return request_type;
}
var http = createObject();
 
function content(){
	var content = encodeURI(document.getElementById('content').value);
	alert(content)
	http.open('get','content.php?content='+content, true); 
	http.onreadystatechange = function(){
	if(http.readyState == 4){
		var response = http.responseText;
		document.getElementById('test').innerHTML = response;
		document.getElementById('test').style.display = 'block';
		}
	}
	http.send(null);
}
 
 
</script>
<form> 
<table border="1" bgcolor="#CCCCCC" width="10%">
<tr><td colspan="2" align="center"><h2>Add Form</h2></td></tr>
<tr><td colspan="2">
	<?php
		$sql = "select * from `fck`";
		$qid = mysql_query($sql) or die("could not select".mysql_error());
		while($rec=mysql_fetch_array($qid)){
			echo $content_value = $rec['content'];
		}
	?>
	</td></tr>
<tr><td><h4>Content</h4></td><td><input type="text" name="content" id="content" value="<?php echo $content_value; ?>" /></td></tr>
<tr><td colspan="2" align="center"><input type="button" name="button" value="Add" onclick="javascript:content()" /></td></tr>
</table>
</form>
<div id="test"></div>

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