W: GPG Error The following signatures couldnt be verified because the public key is not available

Hello linuxer, do you have got experienced about error like this pic, when type "sudo apt-get update" on terminal.

Don't panic you can fix that. Okkey next follow me...

Go to ubuntu Keyserver and search your error key, you can see sample error on my desktop, yeah my error key A6DCF7707EBC211F next copy and paste that on form input on ubuntu keyserver and ATTENTION, Note while searching for key pre-append the key with 0x. So i searched it for 0xA6DCF7707EBC211F.

Click on the link provided in the pub section. This should take you to page containing the key. It should start with something like Public Key Server -- Get "0xA6DCF7707EBC211F" like this

And next copy paste that, and save it. (you can see my desktop i called key2) okkay now open terminal and go to it key have saved, and type command "sudo apt-key add [your key name saved]" example i have been saved called key2 so type:
sudo apt-key add key2
and then wait respon.

When you see respon like that ya "OK" response, now you are done.

Repeat my tutorials of other keys that might be missing and now you can see the magic ;) no error again when you type "sudo apt-get update"

Okkay see you next tutorials, don't forget to fix error problem your friends by share this tutorials. I hope it can help you full, keep coding and stay learning by doing...

UPDATE:
someone (Алексей Абловацкий) give me simple way to do it, maybe you want to try it. Ok next type command on your terminal like this:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com `sudo apt-get update  2>&1 | grep -o '[0-9A-Z]\{16\}$' | xargs`

or like this:

keys=$(sudo apt-get update 2>&1 | grep -o '[0-9A-Z]\{16\}$' | xargs);sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com"${keys}"

creatorb