LocalLayer PopUp with buttons and CSS

[NatashaManzuiga]

Hi all, I need a popup with a button so I configured the property popup-->infoTemplates-->description with this text:
    "description": "theFieldValue: {CODE}<br><button data-dojo-type=\"dijit/form/Button\"  type=\"button\" onclick=\"javascript:void window.open('url{CODE}.pdf','url code', 'width=1024,height=768,status=0,resizable=0');\">Link to PDF</button>
It perfectly works but my problem is that I'm not able to set the css like
I tried to set class...but I'm always getting a button like this

How can I do to set the correct class for the button?

Thanks,

Naty