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This plugin does not work on those versions of IE.
The first issue is that they do not support addEventListener, and require attachEvent to be used instead; after I modified my local copy to account for this I still go errors about this.async on line 37.
This needs looking at for compatibility with those versions of IE.
Thanks for the report.
Can you send a pull request with your modifications to handle addEventListener? I don't have a machine with IE8 or IE7 anymore, but if you can provide a fix and test them I'm more than happy to accept them.
There is a fairly comprehensive test suite, so you can send the browser to http://locachejs.org/tests/index.html to run them.
Some cosmetic changes and fixes for IE.