javascript - Cannot set a proper alignment for a banner on Facebook Canvas (web player game) -

i trying inject banner inside facebook canvas page, game being displayed. there part of code meant place banner in center of screen, right below iframe contains game. banner, html <img> element, placed inside <div> element:

"banner.setattribute(\"src\",\"https://www.toyboxgms.com/cloverclash/twitchybanner.png\");" + "banner.setattribute(\"align\",\"center\");" + "banner.setattribute(\"id\",\"banner\");"  ... 

if run game outside facebook canvas (mozilla browser), in place. however, once play on facebook, banner gets stuck left side of screen in screenshot, though alignment set "center". know facebook placing game inside iframe , nothing else.

in case, banner can aligned right or left. there simple way change , centrally align it?