Javascript:void(window.open("","_blank","outerWidth=400,outerHeight=200,top=500,left=600,menubar=no,toolbar=no,location=no,personalbar=no,status=no,resizable")) You could use a bookmarklet to open a static URL in a limited window : Without using an add-on you can come close. Getting close to what you want using your current profile without disturbing it: If you do change the icon, you will probably want to change the properties for the shortcut to point to the icon you use. An extension whicht arose from my answer to a stackoverflow question.
TAB SUSPENDER FIREFOX ADDON WINDOWS
Shameless plug: If you want the icon for the window to be different so you can tell the windows apart in the taskbar, you could use: Change Profile's Window Icons. "C:\Program Files\Mozilla Firefox\firefox.exe" -no-remote -P "My Profile Name" -url " page I want to see" Firefox should automatically remember the size and location of the window. By right clicking the mouse in the toolbar area de-select "Menu Bar" and "Bookmarks Toolbar". Adjust the size and position of the window to what you desire. There may be others you could use, but the combination of these two worked when I tested it.
It appears you can not do exactly what you desire, if you want to continue to have the page opened under your normal profile and without having your normal use of that profile disturbed. You can find details of the Firefox "Command Line Options" on MDN.