How to make a "Dont ask me again" Option?

I'm trying to make a Dialog in my website using css3 which pops up if the user is using adblock. The dialog basically asks the user to enable ads on my website but I don't to annoy the user with the dialog popping up each time he/she visits my website so i want to give the use a "Dont show me again" option but i have no idea how to implement this.

Here is an image of the dialog

This is the java script code that detects the adblock user and opens the dialog

<script> window.setTimeout(function(){
  if(adsbygoogle instanceof Array) {

    // adsbygoogle.js did not execute; probably blocked by an ad blocker
    window.location = '#PleaseUnblock'

  } else {
        // adsbygoogle.js executed 
    }
 }, 2000); 
</script> 

This is html code for the dialog

       <div id="PleaseUnblock" class="modalDialog">
         <div style="margin-top: 70px;padding: 5px 12px 13px 15px;width: 380px;">
            <a href="#" title="Close" class="close">X</a>
            <div style="padding: 0; margin: 0;">
               <h1 class="ad-di-title">You Are Using AdBlock &#58;&#40;</h1>
            </div> 
            <div style="margin-left: auto;margin-right: auto;width: 350px;height: 332px;background: url(/assets/please.jpg);background-size: 350px;background-repeat: no-repeat"></div>
            <p class="ad-di-para" style="margin-bottom: 3px;">All content made on WEBSITENAME is free. As you use Adblock, we wont get any revenue  from the content we make. We promise that we will not show annoying ads and we only ask you to enable ads in our site.</p>
             <a style="margin-left: 300px" href="#" class="kbtn">Ok</a>
         </div> 
       </div>