Quickly launch an application for your responsive HTML5 website! Professionally customize it to match your color schemes, logo and branding!

1. User Authentication: Secure login/signup methods such as email/password, social media login (Google, Facebook, etc.).

2. Customizable Templates: The app includes templates or themes that users can choose from to create their site. Allow customization of colors, fonts, layouts, etc.

3. Drag-and-Drop Interface: Included add, remove, and rearrange elements using a drag-and-drop interface.

4. Rich Media Support: The app includes media types like images, videos, audio files, and animations.

5. Responsive Design: The app is responsive on different screen sizes to provide a consistent experience across devices.

6. Widgets and Components: The app includes a library of widgets and components (text boxes, buttons, forms, galleries, etc.) that users can use to build their sites.

7. Preview and Editing Modes: The app include both preview and editing modes so users can see how their site looks while making changes.

8. Publishing Options: The app include a feature to enable users to publish their sites directly from the app to a chosen domain or hosting service.

9. SEO Tools: The app offering a basic search engine optimization tools like meta tags, descriptions, and keyword optimization to help users improve their site's visibility.