When Tasktop Dev is set as the default browser, clicking on links to tasks in another application (ex. instant messaging programs) will automatically open them inside Tasktop Dev. To enable this setting, open the preference page (Window -> Preferences), expand "Tasktop" from the left hand menu, click on the "Windows" sub-page, and check "Set Tasktop as default browser while running."
You can configure Tasktop Dev so that web pages open in an external browser while links to tasks and builds open in Tasktop Dev, or you can configure Tasktop Dev to open all links. Note that links clicked in a browser will not open in Tasktop Dev by default, but, if you use Firefox, you can choose to open them in Tasktop Dev by using the Firebox Integration. (Click on Browse Features under Tasktop <=> icon, and then click "Firefox").
Setting Tasktop Dev as the default browser is only supported on Windows.