While setting the new Git server with gitweb I saw this issue.Generally never seen before,here Gitweb page was not displaying correctly.
You can see the below given screenshot:
To solve this issue ,I only approached to create a .htaccess file in Data Directory of gitweb.
In CentOS the gitweb directory I created inside /var/www/gitweb.
You have to add only these two lines in .htaccess
Now restart the apache once and clear the web browser cache also