For security reasons in the latest version of most modern browsers, http iframes no longer load in https pages by default. What this means is that if you have a page delivered by https: containing an iframe that references an http: page, that iframe will appear blank and a 'shield' icon will appear in the browser bar (varies by browser). This affects 'unmapped' Google Sites because all sites from the domain sites.google.com will always be delivered using https: There are several workarounds are available:
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