How to make transparent background of a gif animation?

You can just use an online editing service like gifmagic.com

You can use the Online Image Editor tool.

You can find this option in:

Wizards --> Transparency.

Working fine!

The best way to create a Photoshop script Alt+F9 would be:

1. Select all
2. Select color
3. Remove this color
4. Unselect all
5. Activate next frame
6. Choose next video step

Then run this script from the first frame of opened animated GIF-file. For 100 frames 100 click of mouse = 30 sec.

File-> Save for WEB.