Well... websites are now prohibited from resizing windows except in limited circumstances, and that seems to affect bookmarklets, too.

Would you consider an add-on such as Firesizer: https://addons.mozilla.org/en-us/fire.../firesizer/ (I haven't tried it myself).

You can still do that via the Scratchpad or the command line in the Web Console if there is an XUL page like about:newtab or about:addons on display.

Bug 565541 - Web sites shouldn't be allowed to resize main window

There are extensions that allow to set the window dimension.

I use PrefBar to do this, but there are others.

• Custom Geometry: https://addons.mozilla.org/firefox/addon/custom-geometry/
• Firesizer: https://addons.mozilla.org/firefox/addon/firesizer/
• ResizeIT: https://addons.mozilla.org/firefox/addon/resizeit/

You can also do this with code in Error Console or via an extension or toolbar button that allows to run code with chrome privileges.

• https://developer.mozilla.org/en/Error_Console

var Cc=Components.classes, Ci=Components.interfaces;
var ps = Cc["@mozilla.org/embedcomp/prompt-service;1"].getService(Ci.nsIPromptService);
var wm = Cc["@mozilla.org/appshell/window-mediator;1"].getService(Ci.nsIWindowMediator);
var nb = wm.getMostRecentWindow("navigator:browser");
var txt = 'width x height';
var obj = new Object; obj.value = nb.window.outerWidth + 'x' + nb.window.outerHeight;
if(ps.prompt(null, 'Resize Window', txt, obj, null, {}) && obj.value){
var vA = obj.value.split("x");
if(vA[0]) nb.window.outerWidth = vA[0];
if(vA[1]) nb.window.outerHeight = vA[1];
}

For the sake of completeness, the Web Developer Extension has a resizer among its many handy tools: Web Developer. (It is a little confusing to have two Web Developer items on the Tools menu, however...)

Thanks for the clarification.

I'll try the add-ons.

BTW, does having a lot of add-ons slow down Firefox loading or are they only loaded when they are used?