I assume you mean one where the background is greyed out. These are commonly called “lightboxes”. A search like this will bring up pages with lists of them for you to try out.
By the way, these things are pretty annoying. When I first visit a page, I want to read what’s on it, not be asked “would you mind completing a survey at the end of your visit?” when my visit has barely just started. It’s off-putting.
1:create a div dom
2:set div style. e.g height,width,background,position,z-index ,boder etc. you should set the “position” attribute is Absolute that It is necessary.
3:get the width and height of document using javascript.and compute the top,left for this div.
4:please append this dom in the document.body.
5:close buttom bind a click event when triggering set this div display is none.