Let's take the Breadcrumbs block as an example. In order to disable breadcrumbs on the Auth and Profiles locations, you need to do the following:

  1. In the administration panel, go to Design > Layouts.
  2. Select the Auth or Profiles location (tab) that you want to disable breadcrumbs on. 
  3. Click the Activate/Deactivate block icon of the Breadcrumbs block.

    4. The block should become lighter.