Usually you get this error while installing joomla in linux server,

Error:  Magic Quotes GPC Off


Need to disable magic_quotes_GPC should be disabled in php.ini or .htaccess file.

You have to create a php.ini file under  joomla directory /installation and add below lines,
magic_quotes_gpc = Off
session.save_path = "/tmp"

If it does not working or you have shared hosts ask to your hosting provider to set magic_quotes_gpc=Off in php.ini file.