I'm new to Linux and Ubuntu so I'm still learning many of the features it has to offer. Today I installed OBS and a icon theme (shadow-icons) and when I run sudo apt-get update I get these errors.
W: The repository 'http://ppa.launchpad.net/kirillshkrogalev/ffmpeg-next/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
W: The repository 'http://ppa.launchpad.net/upubuntu-com/icons/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/kirillshkrogalev/ffmpeg-next/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Failed to fetch http://ppa.launchpad.net/upubuntu-com/icons/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
I've looked all over the web for a solution and can't seem to find one. Only thing I could locate remotely close was commenting out
# deb cdrom:[Ubuntu 16.04.3 LTS _Xenial Xerus_ - Release amd64 (201708$
but alas this helps none and was already commented out before hand. Any help would be appreciated for a solution to this issue. Thanks!