You need a Firefox add-on,video downloadhelper.Video DownloadHelper is a very useful Firefox extension, which allows users to customize file formats and quantities to download and have detection capability to identify the true position of the video or music files,then download to your computer.
Step 1 : Go to here download video downloadhelper extension and installed,
Step 2 : Go to downloadhelper homepage,click for the ‘downloadhelper video search’,
Step 3 :Then roll down the webpage till you get this,
Step 4 : Click ‘install adult video sites search engine‘,then these search engine will install in your Firefox.
Step 5 : You can type in any word for searching adult video,