Gzip Compression got turned on
– Backend got messed up after turning on the Gzip Compression.
This option doesn't work on most websites, and if you turned it on, then you could install Firebug on your Firefox browser, then right click on the Gzip compression text, and choose Inspect element with Firebug.
Open up the code under it, until you find this:
Change the value to 0.
Click on the Console tab, write this code in the bottom, and press enter:
After the second refreshing the backend should show up properly.