If a tweet contains two words that are separated by a dot (or period), Twitter – and the various apps like Tweetdeck – may sometimes interpret that combination as a web address and will auto-convert the words into a clickable link wrapped inside a t.co URL.
This is helpful is most cases because you can safely avoid writing http:// in your tweets and Twitter will still convert all the included web addresses into hyperlinks.
However, if you want Twitter to display URLs in plain text and not convert them into hyperlinks, here’s a simple trick – just replace the period (or dot) symbol in your tweet with its ASCII equivalent (.) and Twitter would display your message without conversion.
For example, if I were to tweet – “is twitter.com down?”, the modified tweet will read like “is twitter.down?” and Twitter will show that link in plain (non-clickable) text.
It’s a simple trick but the only problem is that some apps, like the Twitter app for iPad, do no correctly handle ASCII codes correctly but that should get fixed with time.