Height Of An Iframe

I have inserted a source code form a reseller website and am having trouble with the iframe not being full height of the content page. I created it under website/pages. the page is here and code is below https://www.hivis.co.uk/mugs.htmlCan anyone tell me how to have the page /frame be full page height please


  Hivis    img.wp-smiley,img.emoji { display: inline !important; border: none !important; box-shadow: none !important; height: 1em !important; width: 1em !important; margin: 0 .07em !important; vertical-align: -0.1em !important; background: none !important; padding: 0 !important;}   body.custom-background { background-color: #ffffff; }  @font-face{font-family:EuroMG; src:url(https://catalogue.mugsgalore.com/usersites/fonts/EUROSTILE.ttf);font-weight:normal;}     #ifm { height: 0; width: 0; max-height: 100%; max-width: 100%; min-height: 100%; min-width: 100%; display: block; border: none; } #test{ display: inline-block; width: 100%; -webkit-overflow-scrolling: touch; overflow-y: scroll; overflow: auto; } 
#wpfront-scroll-top-container i { color: #b4e1f3; }

Assuming the id of the iframe is "ifm"


Pure JS