If you got this kind of scary message, you can fix it in 4 easy steps:
STEP 1 - Go To Theme Editor
Go to Appearance -> Theme Editor and click on Theme Editor.
The Editor will open.
STEP 2 - Find: header.php
Find a “header.php” in the right column, and click on it to open:
STEP 3 - Find < head> and < /head>" Text
STEP 4 - Insert a Line with your Adsense Code
The last step is to add a line and paste the Google code:
And that’s all! After you done with this part in your Google Adsense website click on “Review my Site” and hopefully soon your site will be reviewed. Time may vary from few hours to few days,
Good Luck!