How to Install php-mcrypt on Plesk 10.3 / CentOS-6 / PHP5.3.3
yum repolist-----------------------------------repo id repo name statusbase CentOS-6 - Base 6.346elrepo ELRepo.org Community Enterprise Linux Repository - el6 223epel Extra Packages for Enterprise Linux 6 - x86_64 8.351extras CentOS-6 - Extras 17plesk103-base Plesk 10.3 - Base 99plesk103-thirdparty Plesk 10.3 - Thirdparty 3plesk103-updates Plesk 10.3 - Updates 0updates CentOS-6 - Updates 1.185repolist: 16.224-------------------------rpm -ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
yum update
yum install php-mcryptsome times enter 'y' service httpd restartfinish, its works!