Hello Anth, you can resize the window on the button code:
<a href="http://www.yourwebsite.com/mibew/client.php?locale=en" target="_blank" onClick="if(navigator.userAgent.toLowerCase().indexOf('opera') != -1 && window.event.preventDefault) window.event.preventDefault();this.newWindow = window.open('http://www.yourwebsite.com/mibew/client.php?locale=en&url='+escape(document.location.href)+'&referrer='+escape(document.referrer), 'webim', 'toolbar=0,scrollbars=0,location=0,status=1,menubar=0,width=640,height=480,resizable=1');this.newWindow.focus();this.newWindow.opener=window;return false;"><img src="http://www.yourwebsite.com/mibew/b.php?i=mblue&lang=en" border="0" width="179" height="63" alt=""/></a>
Look in this line this part:width=640,height=480,resizable .......and set the size that you want.
For more help, post your question or PM me.