Hacking into fee-pay wifi networks.

Note that this stuff is dishonest and possibly illegal in many. if not all, cases. I provide it here just for information purposes which may be useful in emergencies.
The original article said that putting "?.jpg" at the end of many urls allowed free browsing on many sites.
However, from what I read in the comments there doesn't seem to be too many others for whom the hack worked, even in the airport where the OP discovered it.
A suggested alternative is ping tunnelling which is explained here.