Advertisements are a great way for Web sites that provide free services to help recoup the cost of operation. When ads pop up on YouTube, they're not too much of an issue, and are generally viewed as inevitable. However, if you're trying to find a specific video, waiting through a 20- to 30-second ad each time can become very frustrating. Fortunately for Chrome users there's an extension called Skip ads on YouTube - No illegal block, which allows you to skip the ads and get straight to the video.
Read about it here... Get the extension here!