While Google has come up with great algorithm to serve relevant ads to your site, it's not always foolproof. There are also times where you want to block specific ads from appearing on your site for being competitive with your site's purpose.
To do this, go to
Allow & block ads → Blocking options → Advertisers URLs from your Google AdSense dashboard. On that page, click on the
Block new URLs button.
You will then come to the
Block new URLs window. Make sure you select the AdSense product id that you want to block the ads on.
You can now add the URL of the ads that you want to block from appearing in your AdSense ad unit, one per line. You'll also need to check on the reason on why do you want to block the ads.
Once you're done, click on the
Block sites button and the site you have just blocked will appear in the blocked ads list.
You can copy the URL of the competitive ad without clicking on the ad itself by following these simple steps.
Right click on the ad, and click on the
Copy link address from the menu if you're using Google Chrome, or anything similar if you're using other browser. This will copy the URL to your clipboard.