[TwoD]

I've not used Scriptaculous before, but the syntax looks correct.

Given that we have no idea if the [global] variables

Code:

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and

Code:

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are defined/correct at all, or if something else on the page might be overriding the window.onload event handler;
Effect.Highlight - scriptaculous - GitHub and Effect.Parallel - scriptaculous - GitHub suggests setting the 'sync' option to true on the effects so they won't run as soon as they are instantiated.
Also try to explicitly set the restorecolor option on the highlights as the script has problems reading the original background-color correctly in various browsers.