I was really annoyed when I switched to 1&1, and I noted that images where compressed and HTML and JavaScript were modified.  Especially, as the modification interfered with the functionality of those pages!

I understand why they do that – the idea is to accelerate web traffic, which, in theory, makes happier customers (and lower data traffic).  But I want to have control over this (especially if it breaks functionality).

Fortunately, this is possible (even though not widely announced).  For both Vodafone and 1&1 (which uses Vodafone’s network), this can be adjusted by visiting http://performance.vodafone.de/ from your mobile device.  Works as advertised!