use this code ,this is what it looks like click on the listen button on my page its ok  http://ukadoptionregister.org/st

add code below to a page ,drag custom html box onto your page and then add the below code

<div style="position:relative;height:110px;width:120px;cursor:pointer" onclick="window.open('http://www.radioplayer.co.uk/listen/', 'UKRadioPlayerPopup', 'toolbar=0,scrollbars=0,location=0,statusbar=0,menubar=0,resizable=0,width=380,height=660');" onmouseover="document.getElementById('rpgba').style.display='block';document.getElementById('rpgbb').style.display='none';" onmouseout="document.getElementById('rpgba').style.display='none';document.getElementById('rpgbb').style.display='block';"><img id="rpgba" style="position:absolute;top:0px;left:0px;display:none" src="http://www.radioplayer.co.uk/wp-content/themes/radioplayer/img/ukrp-gen-button-sel.png" alt="UK Radio Player Button" /><img id="rpgbb" style="position:absolute;top:0px;left:0px" src="http://www.radioplayer.co.uk/wp-content/themes/radioplayer/img/ukrp-gen-button.png" alt="UK Radio Player Button" /></div>