CSS Layout

p [ attrname ] {..}
p [ attrname = "value" ] {..}
p [ attrname ~= "value" ] {..}
p [ attrname |= "value" ] {..}
p [ attrname1 ~= "value1" ] [ attrname2 = "value2" ] [ attrname3 ] {..}

Selection based on whether:

element has a certain attribute
element has a certain attribute with a specific value ( = )
element has a certain attribute whose value is a space separated list (ie class) and one item is the specific value ( ~= )
element has a certain attribute whose value is a hyphen separated list and first item is the specific value( |= )
element has all the attribute/value combinations specified