Here you,
$('#outerdiv div:not(#innerdiv2)')
with external div enabled:
$('#outerdiv div:not(#innerdiv2),#outerdiv')
This is a valid CSS3 selector; it also works in jQuery.
To answer your comment, I did a little test in the browser console:
a = $('<div id="a"><div id="wrap"><div id="one"></div><div id="two"></div></div>')
a.find('div:not(#two)').addClass('a')
Result:
<div id="wrap" class="a">
<div id="one" class="a"></div>
<div id="two"></div>
</div>
html() HTML . : [#outerdiv, div, # innerdiv1]. , html() html #outerdiv. HTML #innerdiv2, :
$('#innerdiv2').detach()
$('#outerdiv').html()