I just added
width:auto;
to
#access ul ul a {}
and it is a step further in the right direction!
However, the backgrounds of the sub menu list items still don’t line up!
I have only tested this is Firefox 26.0 and it works! Remember, I am using a child theme of Twenty Ten. I simply added the following to my editor style.css:
#access ul ul {
width: auto;
}
#access ul ul li {
width:100%;
}
#access ul ul a {
white-space: nowrap;
width:auto;
}