No problem. lastpage (or _lastpage), is the id of the last page the player loaded while logged in as a GM. It can be blank (don't recall if it's undefined, empty string, or null) if the game is new or the player has never loaded a page as a GM. It can also be wrong if the GM has more than one copy of the game open and they've loaded another page more recently in the other tab. Both those cases are rare occurrences, but you should know about them just in case you run across them.