Drupal 6.x : How to hide blocks?

1. Go to Home> Administer > Site buildings > Blocks
   
   
2. Choose block you want to configure > Click configure
   
   
3. Go to Custom visibility settings:
   Users cannot control whether or not they see this block.

   Show this block by default, but let individual users hide it.

   Hide this block by default but let individual users show it.
   
   
4. Save blocks.
   
   
5. Refresh browser and see the changes . Done