By default Pop-up blockers feature is enabled in Chrome browser on Nexus 7 tablet. It automatically prevent from pop-up windows. But sometime it may cause Wifi Authentication issue or web apps not working.
How to Disable Google Chrome's Pop-up blockers on Nexus 7
* Touch Chrome app and tap the built-in Menu button.
* Touch More "Settings", uncheck "Block pop-up windows" to disable the pop-up blocker. Now you should be able to make use of pop-up windows.