The Pop-up Blocker feature in Microsoft Internet Explorer 6 for Microsoft Windows XP Service Pack 2 (SP2) protects users from malicious activity that is often hidden behind or initiated by pop-up windows. Designed to give users more control over their Web browsing experience, this feature is on by default, and blocks script-initiated pop-up and pop-under windows that launch automatically from a Web site. By understanding how the Pop-up Blocker works, you can ensure that important information on your Web site gets noticed, and you can provide your users with a better Web-browsing experience.

This document assumes that you are familiar with Dynamic HTML (DHTML) and scripting.

This topic contains the following sections.

• Why Do We Need a Pop-up Blocker?
• What Does the Pop-up Blocker Block?
• What Doesn't Get Blocked by the Pop-up Blocker?
• How Can You Ensure That Your Web Site Works With the Pop-up Blocker?
• What Else Do You Need to Know About the Pop-up Blocker?
• Related Topics

Why Do We Need a Pop-up Blocker?

There are many ways in which pop-up windows have been used either to annoy users or to hide malicious activity. Some of the most annoying pop-up window actions include windows that continually reopen when the user closes them, pop-ups that blanket the desktop with banner ads and cover the entire usable space, or pop-ups that keep reappearing, spawned from an offscreen or hidden window. Probably one of the most annoying actions is the pop-up window that appears suddenly and blocks the user's screen, with no visible way to close the window.

Malicious scripts carry out disruptive activities, such as creating pop-up windows that attempt to imitate a user's desktop and then remain in focus, creating pop-up windows that cannot be closed, or creating pop-ups that appear offscreen where they go unnoticed. These activities often hide malicious activity running behind the pop-up window.

What Does the Pop-up Blocker Block?

The Pop-up Blocker blocks script-initiated pop-up windows that are created by the following methods, without the user clicking a link. If users enable the most restrictive setting in the Pop-up Blocker Settings, the Pop-up Blocker blocks windows that are opened by these methods from a user-initiated action, such as clicking a page element or tabbing to a link and then pressing ENTER.

• window.open
• window.showHelp
• window.showModalDialog
• window.showModelessDialog
• window.external.NavigateAndFind

In addition to blocking script-initiated pop-up windows, the Pop-up Blocker also blocks

• setHomePage() from launching automatically. This function can be launched only from a user-initiated action, such as clicking a page element or tabbing to a link and then pressing ENTER.
• Scripts from automatically targeting the search pane.
• Windows that are opened automatically from DHTML elements that overlap content on the same page.
• Scripts from calling window.open on an onunload event in an attempt to get the user to stay on a site, or to serve the user one more ad.
• Scripts from targeting and then navigating to a named frame that doesn't exist.

When the Pop-up Blocker prevents pop-up windows from appearing, the action triggers the Information Bar. Users can decide if they want to see the blocked window by clicking on the Information Bar.

For More information..
http://msdn.microsoft.com/library/default.asp?url=/workshop/author/dhtml/reference/methods/open_0.asp

Suresh Behera