[Plugin: WordPress SEO by Yoast] Code Google webmaster can not be used on Plugin WordPress SEO by Yo

You need to add the full meta tag

<meta name="google-site-verification" content="gLPGcdloe9v32HVTdGE0JtuzpYm8ihOZWbb2ydtI" />

Sorry – are you trying to add/verify your site with Google Webmaster Tools or something else?

To verify with Webmaster Tools, sign in to http://www.google.com/webmasters/
Then click the “Verify this site” link by the site you would like to verify and click the “Alternate Methods” tab.
Select the radio tickbox to “Add a meta tag to your site’s home page”

Then copy the whole line starting “<meta” and ending “/>” and paste it into WordPress >> SEO >> Dashboard >> Webmaster Tools.

Clear any chache plugin you run such as W3 Total Cache or WP Super Cache.

Then click the verify button in Google Webmaster Tools.

Thanks this was exactly what we needed. Thanks!