Very generic issue I am sure, and apologies for the title, but not sure how else to word this.

Background: VisualStudio 2022 preview, .Net 4.8, ASP.Net (not Core)

index.aspx

<asp:Content ID="BodyContent" ContentPlaceHolderID="MainContent" runat="server">
    <style>
        iframe {
            position: absolute;
            border: solid ;
            border-width: 1px;
            box-sizing: border-box;
            min-width: 855px;
            min-height: 465px;
        }
    </style>
    
    <div class="divCanvas">
        <canvas id="compass" height="230" width="230"></canvas>
    </div>

    <iframe id="if1" 
        src="https://awebsite">
    </iframe>
</asp:Content>

CSS

#compass {
    background: url("../images/compass2.png");
    background-size: cover;
    vertical-align: middle;
}

.divCanvas
{
    z-index:99;
    position:absolute;
    margin-left: 525px;
    margin-top: 70px;
}

So what we have here is a simple <iframe> showing me a website and using CSS and <div> I am overlaying a <canvas> object over the iframe, and yes in a specific spot so that it overlays an area of the iframe where I want it displayed, hence the margin-left and margin-right properties.

Problem is, this only works on desktop browsers (all of them), but does nothing other than show the iframe in a mobile browser (all of them again). What's happened with my <div>?

Incidentally, the VS project generated a ViewSwitcher.ascx file, which I think is the issue here, but it doesn't stand out where in the code there is anything happening for mobile browsers.

Any ideas please? Should I be using the ViewSwitcher ascx file in some way to display my div over the iframe? I have no idea what viewswitcher is really doing here in the first place or if it's even needed.

Thanks