jQuery Fancybox Ajax维度

I know how to set dimension width and height on iframe and inline, but i have search for 2 hours now and looking thrue the doc but i cant figure out how to set the dimension to width: 50% and height: 50%

What do you guys say?

'width': '50%',
'height': '50%'

for fancybox v1.3.x, also set

'autoDimensions': false

for fancybox v2.x set

autoSize: false