PowerPoint 2011 shows slide show controls at the bottom left corner during a slide show. In case if you do not want the slide shows controls to be displayed then you can turn off the controls using the options available as part of PowerPoint 2011.
Click the PowerPoint icon and select Preferences from the displayed menu list.
Navigate to Slide show section in View Preferences window.
Set the value for Slide show navigation as [No Slide Show Controls] and this would hide the controls during slide show.