Dear Till,
Thank you for replying.As you know using the hosts file is possible mostly in local station ,but in my case I am trying to do so through SSH and IE.
for example I want to access to my ispconfig :
http://100.100.100.100:81.
As another problem I can point to asking the host name (a valid one) during the installation of ISPConfig(I do not want to assign valid name at the moment).