Ruby has implicit hash parameters, so you could also write
def my_method(options = {})
my_method(:width => 400, :height => 50, :show_border => false)
and with Ruby 1.9 and new hash syntax it can be
my_method( width: 400, height: 50, show_border: false )
When a function takes more than 3-4 parameters, it's much easier to see which is what, without counting the respective positions.