_blank: this target in IE Browser publications creates a popup window (to avoid this behavior, check out the NoAutomaticPopup property). However, HTML Viewer publications won't open a new window but they will display the page in the main window except if the link is external, i.e. http://,ftp://, etc… In fact, for security reasons, you cannot access compiled pages outside a publication. If you want to open a compiled page in a new window, then use _henewinstance.
_hepopup_[name]: opens a new pop-up window whose name is set to [name] (no space, alphanumeric characters only for [name]).
_heexternal: forces the publication to open the destination URL in the default web browser (Internet Explorer or Mozilla Firefox for instance).
_henewinstance: opens a new stand-alone instance of the publication that will display the specified URL.
_heopenit: extracts the file specified by [destination URL] (it must be the virtual path starting from the root without the protocol: MyPath\MyFile.ext) and runs the associated program to open this file. The file is then deleted when the publication is closed.
_hemain: opens the destination in the main window.
Example: this will start a new instance and display “index.htm”: