Pop up window

I have been searching everywhere to find out how to do this. I want to add a popup with fixed attributes for my web applications I am going to create in ColdFusion but I can’t seem to be able to find the right script. I have been able to find some websites with some of the code but I am having a hard time putting it all together.

I know that I will need to call a Javascript for this but when I use the scripts I have found the link opens in a new window and not a fixed size pop up.

I really need help with this because its been a long tims since I have done Javascript and I can’t remember everything.