If you use Google Webmaster Tools to monitor how Google sees your website this is a convenient way of authenticating your site with Google Webmaster Tools.
First, add your site to Google Webmaster Tools.
After entering your Domain Name you will be taken to a screen that shows Recommended Methods and Alternate Methods of verification. Click on the Alternate Methods tab and select the HTML tag option.
A unique meta tag will be generated, copy only the randomly generated number from the code (see screenshot below) not the entire tag and leave this page open. We will be coming back here to verify your site.
Now, head over to your site and go the All in One SEO Pack General Settings screen. Scroll down to the Webmaster Verification section and paste the code into the Google Webmaster Tools field. Make sure you do not include any quotes. Scroll to the bottom of the page and click Update Options.
Go back to the Google Webmaster Tools page that you left open from before and click Verify.
That’s it! Google has now verified your site and you’re free to browse through the different options and information that Google Webmaster Tools have to offer you as a site owner.