Change css width within nested elemetn ?

Change css width within nested elemetn ?

<div dir="ltr"><div>Hi everybody,</div>
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<div>This the code : </div>
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<div>var $.toPrepend = '<div><span></span><a href="#" class="class"></a></div><ul></ul>';</div>
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<div>I would like to know how can change css width of  '<span>'  element ? </div>
<div>Its a new variable create on the fly.</div>
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<div>Thanks,</div>
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