How to remove meta tag in source code?

Try looking in your theme’s header.php template file.

Can’t find the line there… You mean the header.php located in /wp-content/themes/<theme name> right?

Correct.

Ain’t there, anywhere else i can look for it?

Did you use a plugin to add this line?

Yes, i used google’s official Google Publisher Plugin.

Then check what you added via this plugin.

When activating the plugin, it automatically verifies my website with the google account i’m currently logged into. So the plugin automatically adds the line somewhere…

First, identify exactly which plugin you are using and then post in that plugin’s dedicated forum via its page in the Plugin Repository.

I have made a post in the Google Publisher forums, thanks for your help ??