CSS (ie different to ff)

Hi,

Trying to customize this theme https://www.adivorblog.com/ (been given permission to do so) in a virtual machine. At the moment just changed colours but want to move the search form down to the black menu bar and it be fixed to the right hand side.

Have altered the below
#header .f_search { float: right; padding: 156px 17px 0 0; }
to 156 and on firefox it shows correctly over the black menu bar. On IE however it places the search form higher up than the black bar with what ever the background colour is set to.

Any ideas please?

Thanks