Pop-up windows can be divided into two categories: the auto pop-up and the interactive pop-up. The former is notorious for its use of forcing onto visitors commercial messages, polls, and other messages. Pop-ups of this kind are either displayed when the page is visited or when the page is left (exit) beyond control of the user. Most exit pop-ups trigger new pop ups on closing so quite often it is a race between the visitor closing and those annoying windows opening. Due to the fact of major use for commercial purposes a lot of so-called "pop-up blocking programs" are in use today. Also the well known browser Mozilla and browsers based on Mozilla, like Firefox, have the option to block pop-ups. Most visitors not using blocking software are so used to closing auto pop-up windows that even a pop-up window containing for example a navigation menu (remote control) risks being closed before a good look has taken place.
Because pop-ups are often closed on first sight they sometimes pop-up behind (pop-under) the window containing the page that spawns them.
Interactive pop-ups are used for example to display larger versions of an image
or help. However when a new window is required the abilities of the browser can
be used. Sometimes visitors end up with an error because an URL of the form
javascript:some_function() can't be handled by browsers. If a new
window really is desired, remark this near the link or the button, especially
when this is done using JavaScript.
When you decide to use pop-ups make sure that there is always an alternative available for people who have JavaScript disabled, block pop-ups, or use a browser with no JavaScript support. Those pop-ups are called friendly.
The following code shows the wrong way of creating a pop-up:
<a href="javascript:window.open('file.html');">Click here
to open pop-up</a>You can turn the above bad code into a friendly pop-up by moving the JavaScript into the OnClick attribute:
<a href="file.html" onClick="window.open(this.href);
return false;">Click here to open pop-up</a>If JavaScript is disabled the above link still works. Also since this.href is used, if the link is changed you only have to update the value of the href attribute.