This is a longer line with some more text to see how the line will wrap in container
Stylesheet:

div#container { width: 260px; border: 1px dotted #999; margin: 40px }
span#text { background: red; padding: 0 3em 0 0;}

3em right padding on an inline element adds 3em padding on the last line (as it should), but in Firefox 2.0 it also adds a 3em space from the total text to the surrounding box. Padding-left doesn't have this 'feature'...