• http://forum.joomla.org/viewtopic.php?p=1812872
• http://www.popoever.com/joomla/29-the-cms/48-how-to-fix-the-404-error-of-joomla-article-sef-link
• http://forums.digitalpoint.com/showthread.php?t=76525
• http://forum.joomla.org/viewtopic.php?t=691809
• http://forum.joomla.org/viewtopic.php?t=302658
• http://forums.digitalpoint.com/showthread.php?t=658209

After checking the joomla version or trying to debug by changing the set variables and nothing worked, I have looked for htaccess file. There it was, a file '1.txt' which I've renamed to htaccess.txt and the website pages were returning the same 404 error. I have changed the file to .htaccess and the website worked.