Captions in 2.6 not displayed

Have upgraded to 2.6 and inserted the caption code (Otto quoted elsewhere) into my theme style sheet. Still, no captions show up. I have a feeling I might have non-standard code in the style.css, although it works well otherwise (without captions). For images, style.css code is:

img
{
	border:#c99 0px solid;
	padding:1px;
}
img.wp-smiley, img.noborder
{
	border:0;
	padding:0;
}
.left
{
    float:left;
    margin:5px 15px 3px 0px;
    padding:0;
}
.right
{
    float:right;
    margin:5px 0px 3px 15px;
    padding:0;
}

For every image I post, I change “alignright” to simply “right”. Could this be the reason that captions are not showing up? If so, what should I do? Also, is it correct that all old images that have alt text should now have their captions displayed without doing anything? Mine are not displayed.
Thanks in advance!
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