Export a path from AI to png

To export a path from AI (CS5)  do the following:

See also http://creativedroplets.com/transparent-png-with-illustrator/

Select the path(s) you want to export

Copy and paste it somewhere if necessary

Draw an artboard somewhere with the artboard tool

In the artboard presets select fit to artwork

Now export as png and check the box ‘use artboards’

Select your artboard

Select the correct resolution (if the resolution is different from the AI source, the png size will change accordingly)