406 not acceptable error on form submit - php

Question

I have web script that shows
406 Not Acceptable Error
An appropriate representation of the requested resource /admincp/settings.php could not be found on this server.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."
Problem is it works on some hosting providers. Can anyone tell me why is this error coming
<?php
$act=isset($_GET['act'])?$_GET['act']:"";
if($act=='sub'){
$name = $mysqli->escape_string($_POST['site']);
$siteurl = $mysqli->escape_string($_POST['siteurl']);
$keys = $mysqli->escape_string($_POST['keywords']);
$desc = $mysqli->escape_string($_POST['descrp']);
$email = $mysqli->escape_string($_POST['email']);
$active = $mysqli->escape_string($_POST['active']);
$template = $mysqli->escape_string($_POST['template']);
$mysqli->query("UPDATE settings SET name='$name',siteurl='$siteurl',keywords='$keys',descrp='$desc',email='$email',active='$active',template='$template' WHERE id=1");
if($_FILES["file"]["name"]!=''){
move_uploaded_file($_FILES["file"]["tmp_name"], "../images/logo.png");
}?>
<div class="msg-ok">updated successfully.</div>
<?php }
if($settings = $mysqli->query("SELECT * FROM settings WHERE id='1'")){
$setrow = mysqli_fetch_array($settings);
$name=$setrow['siteurl'];
$settings->close();
}else{
printf("Error: %s\n", $mysqli->error);
}
?>
<form action="settings.php?act=sub" method="post" enctype="multipart/form-data">
<label class="artlbl">Site Name</label>
<div class="formdiv">
<input type="text" name='site' value='<?php echo $setrow['name']?>'/>
</div>
<label class="artlbl">Logo (182px x 47px)</label>
<div class="formdiv">
<input type='file' class="file" name='file'/>
</div>
<div class="clear"></div>
<label class="artlbl">Site URL (without "http://" and end "/")</label>
<div class="formdiv">
<input type="text" name='siteurl' value='<?php echo $setrow['siteurl']?>'/>
</div>
<div class="clear"></div>
<label class="artlbl">Meta Keywords (Separated by Commas)</label>
<div class="formdiv">
<textarea name='keywords' cols=40 rows=5 ><?php echo $setrow['keywords']?></textarea>
</div>
<label class="artlbl">Meta Description</label>
<div class="formdiv">
<textarea name='descrp' cols=40 rows=5 ><?php echo $setrow['descrp']?></textarea>
</div>
<label class="artlbl">Email</label>
<div class="formdiv">
<input type="text" name='email' value='<?php echo $setrow['email']?>'/>
</div>
<label class="artlbl">Approve</label>
<div class="formdiv">
<select name="active" id="active">
<?php if ($setrow['active']==1){?>
<option value="1">ON</option>
<option value="0">OFF</option>
<?php }else{?>
<option value="0">OFF</option>
<option value="1">ON</option>
<?php }?>
</select>
</div>
<div class="clear"></div>
<label class="artlbl">Template</label>
<div class="formdiv">
<select name="template" id="template">
<option value="<?php echo $setrow['template'];?>"><?php echo ucfirst($setrow['template']);?></option>
<?php
foreach(glob('../templates/*', GLOB_ONLYDIR) as $dir) {
$TemplateDir = substr($dir, 13);
$TemplateName = ucfirst($TemplateDir)
?>
<option value="<?php echo $TemplateDir;?>"><?php echo $TemplateName;?></option>
<?php }?>
</select>
</div>
<div class="clear"></div>
</br>
<div class="formdiv">
<div class="sbutton"><input type="submit" id="submit" value="Update Site Settings"/></div>
</div>
</form>

Answer 1

<select name="active" id="active"> , can you change name as well as id to something other than active , as active is a keyword.

Answer 2

this problem is caused by apache's mod_security, it scan the request and block it if it contain links.
try to submit this value of $_POST['siteurl'] without the http:// part, that will solve the problem in that case, but you should still contact your hosting provider about that issue.