script for chat application is not working

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Javascript

Hello All,

I have a script that is send by salesforce.com.This script is for live chat.I am calling this script on home Master page on on onclick event of tag.this script is not working.when I click on button and call it this script goes to undefined loop.

The script is as follows:

<script type="text/javascript" language="javascript">
        function chatNow() {
            var __ALC_BADGE_SUFFIX = (Math.round(Math.random() * 1000000000));
            document.write('<a href="javascript://chat" onclick="_alc.startChat(14803); return false;" id="__ALC_BADGE_ONLINE' + __ALC_BADGE_SUFFIX + '" style="display: none">' + decodeURIComponent("<b>Chat Now</b>") + '</a><span id="__ALC_BADGE_OFFLINE' + __ALC_BADGE_SUFFIX + '" style="display: none;">' + decodeURIComponent("<b>Chat Offline</b>") + '</span>');
            if (typeof (__ALC_Badges) == 'undefined') __ALC_Badges = new Array();
            var __ALC_BUTTON = new Object(); __ALC_BUTTON.id = '14803'; __ALC_BUTTON.available = '__ALC_BADGE_ONLINE' + __ALC_BADGE_SUFFIX; __ALC_BUTTON.unavailable = '__ALC_BADGE_OFFLINE' + __ALC_BADGE_SUFFIX; __ALC_BUTTON.department = 11227; __ALC_Badges.push(__ALC_BUTTON);
            return false;
        }
</script>

I am calling this script function on:

<li class="chat_now_icon"><a class="chat_Now" href="javascript:" onclick="chatNow()"></a>Chat Now&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</li>

But it doesn't work.