new window



I want to open a chat room in a new window using:
|<a href="javascript:MDM_openWindow('$CONST_LINK_ROOT/chat.php?$sess_id')" cl***="memlogin">My Chat Room</a>
but the window I get depends on the computer used to open it. On one computer I got a full window but not resizable and shifted 2" to the right. On another one I got a small, resizable window that had to be manually adjusted to see the content.
I tried to enter some features (width, heigh, resizable) but it is not working. The window will not open at all.

What I want to obtain when I click on this link is a full, resizable window not shifted to the right (like a new Internet window) regardless of the computer used.

Another problem is that sometimes the window is blocked and I get the message "Pop up window blocked". Do you know how can I solve this problem? I know how to do it on my own computer but I would like to solve the problem for all users that can access my chat room.
Thank you,
You can't do nothing (in your code) to prevent the window blocking to happen.
Please take a look at this.
Also if you make a little search on the net you'll find lots of articles/tutorials that shows how to personalize that "new windows".