Question: I'm trying to make my header full width but I don't know why it doesn't work, the high is perfect but I don't know what's wrong with the width,
I would appreciate it if you can help me, this is what I have tried:

```
#header {
  width:100%;
 -webkit-background-size: contain;
  -moz-background-size: contain;
  -o-background-size: contain;
  background-size: contain;
  padding-bottom: 9%;
  background-repeat: no-repeat;}

```

Thank you.

Answer: 
I had a similar problem when launching Firefox version 52.3.0 with X11 forwarding on CentOS 7 :

*WARNING: pipe error (35): Connexion ré-initialisée par le correspondant: file /builddir/build/BUILD/firefox-52.3.0/firefox-52.3.0esr/ipc/chromium/src/chrome/common/ipc\_channel\_posix.cc, line 322*

And same error (in french) on firefox "Gah, you tab just crash"

To correct this, i tried first to update all the package without success.
So i combined two solutions i found on the net :

1- I opened the "about:config" page (just type about:config in the url field then enter) and changed to "false" the 2 options browser.tabs.config.autostart and browser.tabs.config.autostart2

2- I opened the "about:support" page and click on "Repair Firefox..."

Then it works ! but i still have the following problem : i need to do this each time i relaunch firefox; So i should not close all tabs.
Check your SELinux configuration. In special check that `mozilla_plugin_can_network_connect` is enabled. You can do: `getsebool mozilla_plugin_can_network_connect` if answer is `off` then do `setsebool -P mozilla_plugin_can_network_connect=1`. Then try again `firefox&`