Gravity Form Css not Working with Form Lightbox Pop-up

hi,
i`am using form lightbox plugin and i want to use gravity form with a pop-up page. how can i set gravity forms css settings with form lightbox pop-up.

you can check this matter on my site.

http://www.exceltr.com/

the pop-up opens when you click the url with named "soru sormak icin tiklayin!"

Thank you very much Rob, its working spectacular.