If a user downloads anything by code below

Filedownload.save(new AMedia(destFile, "xlsx", null), getImportExportDataSourceName());

an iframe with id zk_download is created. But this iframe is created with visibility:hidden property.
It should be display:none IFrame is never lost. Stays there after download or during download. And creates an annoying scrollbar on the right. I have shared both firefox and chrome screen-shots.