Common Pop-up Blockers in IE

A really useful summary from CC.

Internet Explorer Pop-up Blocker

The internet explorer pop-up blocker has three settings which determine how strict the pop-up blocker is. These settings are as follows:

• Low – Allows all pop-ups besides those not caused by user interaction. Those not caused by user interaction, but from a secure website are allowed. This appears to allow all MLS pop-ups to show.
• Medium – Allows all pop-ups caused by user interaction. Pop-ups opened by window events, or used in script blocks are blocked. Most MLS pop-ups are allowed with this setting. This is the default setting of the IE pop-up blocker.
• High – All pop-ups are blocked indiscriminately.

What IE Considers a Pop-Up

The following javascript methods trigger IE to block the Pop-up:

• Window.open() *Used by the MLS
• Window.showHelp()
• Window.showModalDialog() *Used by the MLS
• Window.showModelessDialog()
• Window.external.NavigateAndFind()

In addition, the following will trigger IE to block the Pop-up:

• Windows that are opened automatically from DHTML elements that overlap content on the same page.
• Scripts calling window.open on an unload event in an attempt to get the user to stay on the site.
• Scripts targeting and then navigating to a named frame that doesn’t exist.

Exceptions to the rules above include:

• Pop-up is opened by a link the user clicked (Does not apply in High).
• Pop-up is opened on user-initiated actions, by ActiveX controls that are instantiated from a Web site.

• Pop-up launched from a Web site on a user's allow list. Users can add Web sites to their allow list through the Pop-up Blocker settings or opened from the Trusted Sites or Local Intranet zones.

For more information on these rules see the MSDN Article

Google Pop-Up Blocker

The Google Pop-Up Blocker behaves in the same way as the IE pop-up blocker on the default (“Medium”) setting. The IE pop-up blocker, however, takes precedence over the Google Pop-up blocker, so if set to Medium the IE Blocker will block before the Google toolbar has the chance.