how do i unblock a blocked web site

Do you use any addon to block pages?

Is this about blocking a plugin?

You can inspect and manage the permissions for the domain in the currently selected tab via these steps:

• Click the "Site Identity Button" (globe/padlock) on the location bar
• Click "More Information" to open Page Info
• Go to the Permissions tab
• Tools > Page Info > Permissions

• https://support.mozilla.org/kb/how-do-i-manage-website-permissions

If you see any notification icons in the address bar to the left of the site address, click those for more information:

• gray shield (see also: Mixed content blocking in Firefox)

• Lego-like icon (plugin notification)