The documentation for css() says that setting the style property to the empty string will remove that property if it does not reside in a stylesheet:
Setting the value of a style property
to an empty string — e.g.
$('#mydiv').css('color', '')— removes
that property from an element if it
has already been directly applied,
whether in the HTML style attribute,
through jQuery’s.css()method, or
through direct DOM manipulation of the
style property. It does not, however,
remove a style that has been applied
with a CSS rule in a stylesheet or
<style>element.
Since your styles are inline, you can write:
$(selector).css("-moz-user-select", "");