I too used to have this problem while using my old Motorola Atrix from time to time. It would usually last a few hours and then have no issues for several months. The t.co url is a wrapper/shortening service provided by Twitter. Occasionally there would be issues with the service being slow/down and not redirecting properly for me, thus the page would just hang on the t.co screen. I was never able to pin down exactly why it would happen but I've never had it happen on my GS3. How long has it been happening for you?
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