If you want an inexpensive and simple mask, you've come to the right place.
Step 1: Materials
You'll need duct tape, a piece of card stock or cardboard, scissors, a plastic bag(from any local grocery store), a black sharpie, and some imagination.
Step 2: Form
First, carefully put the plastic bag on your head (with adult supervision)and pull it tight, then poke eye and nose holes into it so you don't suffocate. Then, while it's tight, wrap duct tape around your forehead so that it is secure. Next cut below the nose and go all the around so that it won't limit your breathing and it will be better to work with.
Step 3: Duct Tape
Wrap the duct tape around it so that it fits nicely and will be easy to slip off.
Step 4: Face Plate
Cut out eyes on the card stock and cut a small slit on the top in the middle. DON'T cut out the nose and mouth like I did, I got carried away. Then where you cut on the top, staple or tape it together so that it creates an angle.
Step 5: Duct Tape Face Plate
Duct tape the face plate and attach it to the head piece.
Step 6: Webbing
Use a sharpie to draw the webs on or find a large piece of mesh and glue it on the mask. I decided to use thin pieces of duct tape for the webbing.
Step 7: The Eyes
If you want make the lenses, visit moyeongsu's page. If you want The Amazing Spiderman glasses, visit eBay or go to Party City and pop out the lenses.
Step 8: Finished!
Now you have an amazing spiderman mask for parties, contests, and even Halloween! If you found this instructable helpful, vote, comment, and follow me! If you want to suggest a costume(in the marvel/dc category) please do. Thx!