O2 UK mobile users - your operator is breaking this site for you.

In a comment to a previous blog post on iPad/iPhone, Steve notified us that aprs.fi often does not work on the iPhone when used on the O2 UK 3G mobile carrier. It works fine on the same iPhone when he switches from 3G to a Wi-Fi connection.

Well, it turns out that O2 in the UK is running a transparent proxy server which compresses and modifies the web pages in many ways. Their intention is to make the pages smaller so that they would use less of their valuable radio bandwidth, but they ending up breaking the web experience really badly for their users. Here's what they do (information from Stuart Roebuck's blog and O2 user forums):

They re-compress images so that they look ugly on a device which has a bigger screen (such as the iPad, or a laptop connected to the iPhone).

Their proxy downloads CSS and JavaScript files and inlines them inside the HTML page before returning the HTML to the customer's phone. Normally the CSS and Javascript would be downloaded to the phone once when the first page from aprs.fi is downloaded, and after that they would be cached in the phone's memory so that they would not be downloaded again with the following pages. Now they're downloaded again and again with every page.

The CSS and JS code is actually much larger than most of the HTML pages downloaded from this site!

The inlining actually increases bandwidth usage (thus increasing your mobile data charges), slows down this web site, and often makes it unusable, because it breaks the HTML encoding and quoting rules for characters like < >. Steve's iPhone usually refuses to render the pages from aprs.fi due to this.

The inlining also removes comments, which might contain things like copyright clauses and software licenses. I suppose it's illegal to remove those.

For more information, please see Stuart's fine blog posts regarding the matter. I suppose the best options right now are (1) complaining to O2 about this, and (2) switching to another carrier, such as Three.