Error on Pre-Installation check

[rastermedia]

I get this error

 Session save path      /var/lib/php5,
Warning: is_writable() [function.is-writable]: open_basedir restriction in effect. File(/var/lib/php5) is not within the allowed path(s): (/var/www/vhosts/aigiorama.gr/httpdocs:/tmp) in /var/www/vhosts/aigiorama.gr/httpdocs/el/installation/index.php on line 256
Unwritable

I have checked permissions and they are OK. What should I do? Important: I'm a neewbie with databases; please be as specific as possible.

Also, there is something that worries me: is the configuration.php the same file with configuration.php-dist which is included in the package or not? Do I have to rename it?

Thanks

[Ivan Trebješanin]

First: This looks as read/write permissions problem to me.
Second: configuration.php-dist should be renamed to configuration.php, after pasting the code given by the installer into it.
Third: You forgot to  post a link to your site. 
Fourth: Is your server running in safe mode?

[datahell]

Your host has enabled open_basedir restriction but the session save path is unwritable. This sounds like bad server configuration. If you have the permisions you can set an other session save path for your domain via an htaccess file. Contact your host for support. You pay them for the hosting...