Go to Options, then into Specials. Select Cheats and enter one of the following codes you can find below:
Invincibility: NERGETS
Infinite Webbing: FILLMEUP
All special moves: MYHERO
All levels: WARPULON
All movies: POPPYCORN
All production art: SHUTT
Storyboard viewer: FRZFRAME
Tiney spiderman: SPIDEYMAN
Spidey has big head and feet: HEAVYHEAD
Enemies have big head and feet: BAHLOONIE