
You have to just take an iframe and passed the name of the iframe to startchatwithwindow
<iframe name="myiframe" style="height:300px;">
Here we show the chat window.
</iframe>
<script type='text/javascript' src='https://c.la10.salesforceliveagent.com/content/g/js/36.0/deployment.js'></script>
<script type='text/javascript'>
liveagent.init('https://d.la10.salesforceliveagent.com/chat', '57228000000PBN5', '00D280000019WTn');
</script>
<a id="liveagent_button_online_57328000000PBP1" href="javascript://Chat" style="display: Block;" onclick="liveagent.startChatWithWindow('57328000000PBP1','myiframe')"> Online </a><div id="liveagent_button_offline_57328000000PBP1" style="display: block;"> Offline Chat Content</div><script type="text/javascript">
if (!window._laq) { window._laq = []; }
window._laq.push(function(){liveagent.showWhenOnline('57328000000PBP1', document.getElementById('liveagent_button_online_57328000000PBP1'));
liveagent.showWhenOffline('57328000000PBP1', document.getElementById('liveagent_button_offline_57328000000PBP1'));
});</script>