now it workes in firefox

template/css/frames.css

@@ -16,7 +16,7 @@ body {
 
 #container {
   display: grid;
-  /*grid-template-rows: repeat(var(--grid-rows), 1fr); not working in Firefox*/
+  grid-template-rows: repeat(var(--grid-rows), 1fr);
   grid-auto-rows: calc(100vh/var(--grid-rows));
   grid-auto-columns: calc(100vw/var(--grid-cols));
   grid-template-columns: repeat(var(--grid-cols), 1fr);

template/js/ui.js

@@ -70,7 +70,7 @@ function makeFrame(lx, ly, rx, ry, content = "", id = "", defaultpara = "", show
         fullurl = fullurl.slice(0, -1);
       }
 
-      $(".item" + lx + "-" + ly).html("<iframe name='" + id +"' id='" + id +"' src='" + fullurl + "' title='' frameBorder='0' ></iframe>");
+      $(".item" + lx + "-" + ly).html("<iframe style='height: 100%; width: 100%' name='" + id +"' id='" + id +"' src='" + fullurl + "' title='' frameBorder='0' ></iframe>");
 
       if(showbutton){
         $(".item" + lx + "-" + ly).append('<button class="formbutton" type="button" onclick="sendForm(\'' + '.item' + lx + '-' + ly +'\', \'' + encodeURIComponent(id) + '\', \'' + lx  + '\', \'' + ly  + '\')">' + showbutton + '</button>')