This post is all about a very common design element that I really hate (most of the time).  I'm talking about modal dialog boxes (or modal windows).

In UI terminology, a dialog box is a window that pops up and prompts some action from you.  They can be used to confirm that you want to delete something, to enter a password, or to give you a status update among other things.  The term "modal" means that this window takes the focus so that you can't interact with anything else in the application until you address whatever action the dialog box is calling for.

Dialogs and pop-up windows are fine, but when you make them modal you're really limiting how a user can work with the software.  Microsoft Outlook is the worst with this.  Almost anything you want to do in outlook other than reading an email causes a modal window to pop up.  If you need to edit your signature, change your account information, or configure plugins, you can't interact with anything else in outlook.  This is particularly frustrating when you want to copy text from an email into your signature (which happens more than you might realize) but you can't view any emails when the signature editor is open.

If you're not sure what I'm talking about, try this (you'll need firefox and chrome):

• Open firefox and to to tools > options
• With the option window open, try going to a new web page in the web browser.
• Now try it with chrome.  Open the options and try to go to a website.

Modal dialog boxes are slightly more necessary with web development.  Websites have the problem that a pop-up in a window can't exist if a new page is loaded, so it makes sense to lock down the rest of the window to prevent the user from clicking links.  To be clear, I'm talking about javascript/html pop-ups within the parent window, not new instances of the browser.