After you download the Design Extender ZXP file from our site, don't double click it to start the install, instead, open the extension manager, in the extension manager click the install button and browse to the downloaded ZXP file.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.