So what's the opposite of a dirty trick?

那么诡计的相反一面是什么。

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A favorite dirty trick: making anonymous phone calls to the IRS, accusing enemies of income-tax cheating and thereby inducing the IRS to audit them.

他们最喜欢用的卑鄙手段是：给国税局打匿名电话，指控自己的敌人在所得税上存在欺诈行为，从而引得国税局去对他们进行审计。

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A dirty CSS trick allows you to hide the text and show a picture in the browser.

一个复杂的CSS技巧可以在浏览器中隐藏文本显示图像。

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The 'Dean scream' dirty trick which, as you know, was created by filtering out the deafening crowd's roar to create the false impression of a maniacal yell (a sound clip used to this day during the Political Junkie segment on NPR's Talk of the Nation).

NPR: Ready, Ames, Fire: The Iowa Straw Poll

One cannot, based on present information, say that this was clearly a dirty trick by the Gore campaign.

CNN: Bill Schneider on the presidential campaign

You cannot say it was a dirty trick by the Gore campaign at this point, although clearly a Democratic activist in Maine had a hand in it.

CNN: Bill Schneider on the presidential campaign