Error: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.20' not found

Solution :
Your gcc is older and you need to upgrade new.

If you are using centos, here is the procedure to upgrade gcc

wget https://ftp.gnu.org/gnu/gcc/gcc-8.1.0/gcc-8.1.0.tar.gz
yum install libmpc-devel mpfr-devel gmp-devel zlib-devel*
./configure --with-system-zlib --disable-multilib --enable-languages=c,c++
make -j 8
make install

docker compose error : ERROR: Service failed to build

ERROR: Service failed to build: Get https://registry-1.docker.io/: Get https://auth.docker.io/token?scope=: dial tcp: lookup auth.docker.io on 127.0.1.1:53: read udp 127.0.0.1:48237->127.0.1.1:53: i/o timeout

ERROR: Get https://registry-1.docker.io: Get https://auth.docker.io: dial tcp: lookup auth.docker.io on 127.0.1.1:53: read udp 127.0.0.1:47094->127.0.1.1:53: i/o timeout

Solution :
Add 8.8.8.8 in /etc/resolv.conf as a nameserver.
nameserver 8.8.8.8

Now try to run 
docker-compose up

You should not get the same error again.

Firefox - Take screenshot of full page

Solution : 1
1. Update with latest Firefox.
2. In right side of the address bar, there is Page Actions menu (three dots)
3. Click on it and select option "Take a screenshot"
4. Either select option full page or visible page.
or
Right click on the page and select option 'Take a Screenshot'
Here you can take screenshot of full page or visible page.

Solution : 2
1. Press key Shift + F2, Firefox console will be visible
2. Run command
screenshot --fullpage
3. It will save screenshot of whole page in default download folder.

Solution : 3
Use addon screengrab