Either Vodafone and T-Mobile use hidden picture compressions and remove alt text inside web pages when you surf with a UMTS stick. The traffic goes through a transparent proxy with that “feature”. Pictures inside browsers have less quality. Most annoying for me is that if you browse on geocaching.com for Geocaches on a map. You see normally the name of the cache if your mouse goes over the cache icon on the map. With a mobile internet connection you see a hint that “Shift-R improves quality of that picture and SHIFT-A improves the quality of all picture on that page”. A solution for this is a firefox plugin called: “Modify Headers“. Go to the extras menu and open “Modify Headers” entry. Enter a new rule and in the first field (Name) “Cache-Control” and in the second field “no-cache” (Value). Save the rule and enable them. Restart the browser. Now reopen with firefox a page with pictures. Quality as with normal internet connections and no more annoying hints to improve quality. In geocaching.com maps will now the name of the cache presented as expected.