Dialogue box for .NET site

I'd need a widget to be displayed in a .NET site when the user browses in it. The widget needs to fit into these features: 1. Widget's content (pics and text) can be edited by myself using a unique console with multiple widgets 3. Possibility to upload pictures (small logos) 4. Responsiveness 5. Possibility to change colours of the widget 6. Possibility to add a customizable button to an external link This widget can be closed and open by the user. When closed, a small "flap" will come out from the side of the monitor. This flap will follow the user when scrolling up or down and when visiting the rest of the site. The widget will scroll down with the user when the user scrolls down/up the site. This widget can be a dialogue box. Any other better solution can be suggested.