WTA: How to resolved code that automatically generated with backslash (\) ???

Hi everyone, i need to solve this problem because it makes me dizzy for some last days.
My problem is when I write html code that have quote sign (""), after I click save button, my code will generated automatically with backslash (\). Indeed when I save more than one, the backslash also will add directly.

!DOCTYPE html PUBLIC \\\\\\\\\\\\\\\"-//W3C//DTD XHTML 1.1//EN\\\\\\\\\\\\\\\" \\\\\\\\\\\\\\\"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd\\\\\\\\\\\\\\\">
<html xmlns=\\\\\\\\\\\\\\\"http://www.w3.org/1999/xhtml\\\\\\\\\\\\\\\">
<head>
<meta http-equiv=\\\\\\\\\\\\\\\"Content-Type\\\\\\\\\\\\\\\" content=\\\\\\\\\\\\\\\"text/html; charset=utf-8\\\\\\\\\\\\\\\" />
<title>Untitled Document</title>
<style>

Above code is the example after I click save button more times, anyone please answer the possibilities. It happened because of virus on my server or what? Because when I config using another server, MODx won’t appear this suck code.

Please reply..thank you so much

You need to disable magic_quotes_gpc.

http://php.net/manual/en/security.magicquotes.disabling.php

Thank you Bob. I’ll try to call my host admin to turn it off for me, because when I tried to adding "php_flag magic_quotes_gpc Off" in .htaccess I got Internal Server Error instead.
But, thank you for the enlightenment, I don’t know about magic quotes before.
Thx