table-layout is another CSS property that I think too often goes unmentioned when talking about table based layouts; the default value (auto) is essentially "do something the spec isn't even going to try and define because implementations be crazy because they're essentially reverse-engineered copies of IE6's behaviour which is itself a reverse-engineered copy of NN4's behaviour".

The other value the property can take, fixed, makes table layout way more predictable: with no width properties defined, an n column table will result in each column having an equal width. If you define a width on some columns, it will split the remaining space between the remaining columns. This is far more often what you actually want when laying out non-tabular data using display: table as a make-shift grid layout system.