Probleme

Hello
I can’t identify the conflict i have ob this script, i would like to get image on middle fixed. its not running on ie, probleme on chrome and on mozilla (random behaviours if i reload page ??? so strange) some idea ? http://www.egl.fr/notre-activite/conseil/

https://ww.wp.xz.cn/plugins/full-screen-page-background-image-slideshow/