in order to delete a task in the iOS app or the mobile version http://todoist.com/m please
- access the project that contains the task you'd like to delete,
- then scroll down to the bottom of your list,
- click on the "Manage tasks" button,
- then click on the red icon on the left,
- confirm by clicking on the "Delete" button on the right and
- save the changes in the upper-right corner.