restrict link to open same link once again

I have one link example

<a href="xyz.html" target="_blank">Click Here</a>

When ever i clicks on "Click Here" I can able to open new tab opens with xyz.html page.

My problem is if I have already exist the page with same link开发者_高级运维, I don't want to open once again.

Is is possible to restrict like this.

please some one help me.

Thanks.

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Set as target a name. The Browser should load the Page in this named Window.

<a href="xyz.html" target="mynewwindow">Click Here</a>