An issue of JQM

An issue of JQM

Hello, My website has both header and footer, which are fixed and not toggleable. I want them stick at the top and bottom of window, no matter what happens. However, in some browsers, when a pop-up dialog with a text input shows, the header and footer become not fixed. They disappear automatically. And when that pop-up dialog closed, they do not show again. The header stick at top of webpage and the footer stick at the bottom of webpage. They should return to the top and bottom of window, right? My question is why not JQM give users a stranger way to force header and footer sticking at the top and bottom of window no matter what happens. The current way is weaker.