Bug: margin-right not asigned 'auto' by default with HTML or BODY
"If none of the properties [margin-right, margin-left, width] are
'auto', the value of 'margin-right' will be assigned 'auto'.", see Horizontal formatting.
If this is honored, the following should not take any effect:
... But with 'auto' the value becomes zero, so there is a change and it wasn't 'auto' before (compared to implizit margin-right when text-align: left (or none et all) is used).