Rowan wrote:
That's an improvement, but I just noticed something else. What if someone's half way down the page and they want to search for anything above where they currently are, instead of only things below where they are?
To solve this you would leave the Previous button clickable at all times, like the Next button.
Good point. Searching could start on the first line visible in the browser, and pressing next at the bottom or previous at the top could wrap around to the other end of the page.
Next would still be the default button when you press enter.
Revision 2: (incorporated an idea from an earlier comment as well):

WinForms makes such a nice prototyping tool...