[quote]I don't think a DOM tree is necessarily all in memory. For performance reasons you might cache the tree in memory, but that's not a requirement.[/quote]

[quote]I don't think a DOM tree is necessarily all in memory. For performance reasons you might cache the tree in memory, but that's not a requirement.[/quote] Yes it is not a requirement. What browser have you heard of storing in the tree in something else than memory? Imagine if the browser used a the disk to store parts of the tree.