I am Getting an Error Unable to set value of the property 'className': Error?

I am setting a class to a different class.

I am doing the coding as follows:
document.getElementById("prevowners-section").className = "subnav-target";

When the new class name is entered, an error occurs:
Unable to set value of the property 'className':  object is null or undefined


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Test page : http://jsfiddle.net/rqLmgjjp/

document.getElementById("prevowners-section").setAttribute("class", "subnav-target");

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Michel PlungjanIT ExpertCommented:
@Leakim: Identical result

document.getElementById("prevowners-section1").setAttribute("class", "subnav-target");

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More likely need is to use
window.onload=function() {

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Michel PlungjanIT ExpertCommented:
Hi, not to be picky, but what was Leakim's contribution to solving your issue?

If the issue was that the prevowners-section was not rendered at the time you executed your script, then the window.onload was the solution.

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