Try "Ctrl+0" (zero) to restore normal size, see if that does anything.

Please provide the url.

Please paste the following into the location bar and report the size of your current window. (will not work from location bar in Firefox 7.0.1 but your version is more practical)

javascript:void(alert("resize:help%20from%20http://www.mvps.org/dmcritchie/firefox/lessons/intro/k.html\nCurrent%20Window:%20"+window.outerWidth+"X"+window.outerHeight+",%20%20%20current%20width:%20"+window.outerWidth+"\nScreen%20Available:%20"+screen.availWidth+"X"+screen.availHeight+"\n%20Full%20Screen%20Size:%20%20"+screen.width+"X"+screen.height+"\n\nscreen.availTop="+screen.availTop+",%20screen.availLeft="+screen.availLeft+",%20screen.availHeight="+screen.availHeight+",%20screen.availWidth="+screen.availWidth+",%20screen.colorDepth="+screen.colorDepth+",%20screen.height="+screen.height+",%20screen.colorDepth="+screen.colorDepth+",%20screen.left="+screen.left+",%20screen.pixelDepth="+screen.pixelDepth+",%20screen.top="+screen.top+",%20screen.height="+screen.height+",%20screen.width="+screen.width+",%20window.outerHeight="+window.outerHeight+",%20window.outerWidth="+window.outerWidth))

Here is a re-ordered version of the above posted bookmarklet.
In Firefox 7 you can run this code via the Scratchpad (Shift+F4)

javascript:void(alert("Current Width: "+window.outerWidth+"\n\nCurrent Window: "+window.outerWidth+" x "+window.outerHeight+"\nScreen Available: "+screen.availWidth+" x "+screen.availHeight+"\nFull Screen Size: "+screen.width+" x "+screen.height+"\n\nwindow.outerWidth="+window.outerWidth+"\nwindow.outerHeight="+window.outerHeight+"\n\nscreen.availTop="+screen.availTop+"\nscreen.availLeft="+screen.availLeft+"\nscreen.availWidth="+screen.availWidth+"\nscreen.availHeight="+screen.availHeight+"\n\nscreen.top="+screen.top+"\nscreen.left="+screen.left+"\nscreen.width="+screen.width+"\nscreen.height="+screen.height+"\n\nscreen.colorDepth="+screen.colorDepth+"\nscreen.pixelDepth="+screen.pixelDepth));