sure you can do the sliding effects like that but keep in mind that since jquery 1.9 $.browser is removed.
So be sure the version you are using is lower than 1.9.Also navigator.userAgent might help you
actually not slide down but the animate function in my pen
if (navigator.appName == ‘Microsoft Internet Explorer’)
tested on IE9 and IE10. `$.browser` is removed as @pixelgrid said, downgrading your jQuery just to get that back seems not like a valid option to me, though if you did… I’m puzzled why it wouldn’t work.
@thedoc, I agree on browser sniffing but for this the worst thing that could happen is the input gets focused for future IE versions if they ever decide to go with Netscape as `navigator.appName` like other vendors do.