Codes Pages: Strange Behaviour

Not related to the program, probably not even a bug as such, but a behaviour I have often found to be a bit of a bugbear!

I use Firefox as my main browser. For some reason when I search for a term (which is obviously something I do a lot as I don’t know the code at all well) and then hit F3 to go to the next occurance of the term it takes me to a different page instead of finding the next term on the page.

EG: from
hitting F3 will take me to:

Not on every press though…

Any idea why? Or what I can do about it?

If I make sure the cursor is in the search field then it will correctly find the next term, if I have clicked on the page anywhere then it will forward me to the above page.