Kevin Godby pointed out that in the Ubuntu-docs case, the <kbd></kdb> tag pair, which is inside most, but not all, <span class" key">...<.span> pairs does actually make a box around the key. For whatever reason "$color.gray_background" compiles into #f7f6f5, which is imperceptibly different than white, and also is not as declared in the color.xslt file ("'#f3f3f0'") (which probably is not grey enough anyhow). Once I took a screen shot and pasted it into photoshop and zoomed in (attached), I could finally see what Kevin referred to. This posting is for completeness only, and doesn't change the need to define "span.key" as per my previous posting.
Kevin Godby pointed out that in the Ubuntu-docs case, the <kbd></kdb> tag pair, which is inside most, but not all, <span class" key">...<.span> pairs does actually make a box around the key. For whatever reason "$color. gray_background " compiles into #f7f6f5, which is imperceptibly different than white, and also is not as declared in the color.xslt file ("'#f3f3f0'") (which probably is not grey enough anyhow). Once I took a screen shot and pasted it into photoshop and zoomed in (attached), I could finally see what Kevin referred to. This posting is for completeness only, and doesn't change the need to define "span.key" as per my previous posting.