DEBES COLOCAR LA PARTE 1 DEL CODIGO EN EL POST O ENTRADA.

CODIGO: PARTE 1 de 2:

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    <div id="Iframe-Liason-Sheet" class="iframe-border center-block-horiz">
       <div class="responsive-wrapper responsive-wrapper-wxh-760x1200">
         <iframe src="https://docs.google.com/forms/d/e/1FAIpQLSfimDXyxTRKMOFRD5eeCIjieG8Vq9vBZbLhKXIO-mPfyyApqQ/viewform?embedded=true">Cargando...</iframe>
       </div>
     </div>

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NOTA: recuerda sustituir la URL de este iframe por la tuya.

LA PARTE 2 DEL CODIGO LA DEBES COLOCAR EN EL PERSONALIZADOR CSS.

CODIGO: PARTE 2 de 2:

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    #Iframe-Liason-Sheet {
    max-width: 760px;
    max-height: 1200px;
    overflow: hidden;
    }
    /* inner wrapper: make responsive */
    .responsive-wrapper {
    position: relative;
    height: 0; /* gets height from padding-bottom setting */
    -webkit-overflow-scrolling: touch;
    overflow: auto;
    }
    .responsive-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    margin: 0;
    padding: 0;
    border: none;
    }
    /* padding-bottom = h/w as a % */
    .responsive-wrapper-wxh-760x1200 {
    padding-bottom: 363.6364%;
    }
    .iframe-border {
    border: 1px solid #000;
    }
    .center-block-horiz {
    margin-left: auto !important;
    margin-right: auto !important;
    }

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