This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
2. tbody sounds like it's a reference to a tbody element, so this is simply traversing the DOM tree. (Would be lots and lots easier using jQuery.)
Start with a tbody element
first child of the tbody would be the first tr element
last child of the tr would be the last cell [td or th]of the table
first child of the cell would be the first element in it.