[jQuery] Problems with selectors and this keyword

[Coxy]

$('.mainTable > tbody > tr').bind("mouseover", function(){
        // alert('hi');
        //$(this + ' > td').css('background', '#ff0000'); // Didn't work
        $(this + ' td').css('background', '#ff0000'); // Doesn't either
});

I want to highlight td's in a row when I mouse over the TR's. I set
the mouseover function using the above code. The alert works when I
mouse over the row, so I then tried to select the TD children and
change their bg but it then does nothing.

Did I use this incorrectly? I'm new to jQuery and am still getting
used to the selectors.

Thanks for any advice.