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First of all, check if your site has mod_rewrite enabled by asking your hosting service provider(assuming you are not using MysidiaHost). The 404 error is usually caused by failure to upload .htaccess file to your server, for some servers or ftp clients it can be a problem. You can go to Cpanel -> File Manager to see if .htaccess exists, and if not you need to upload it. Also keep in mind that for 000webhost, the database host is not 'localhost', you may need to ask them what it is.

BTW, plz do NOT post Mysidia script related topic in the 'Feedback and Suggestions' subforum since it is for site/forum related threads(not for technical support). I moved the thread for you to the correct 'Questions and Support' subforum this time, next time I may just delete it.