How can I write text that the clipboard sees but isn't visible?

Until recently I'd been using style=display:none on an image to do开发者_StackOverflow this with its alt text. That method is no longer working, so what can I do?

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<span style="font-size: 0;">i should still be copied</span>

jsFiddle.

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/* Fully transparent text */
color:rgba(0,0,0,0)