Thanks for your post vekia but it doesn't work for me, i have prestashop 1.6.1.0.
By reading your tutorial i read that i have to open file override/classes/Meta.php but that file doesn't exist by default in my prestashop version....
No matter, i tried creating a new file, named it Meta.php in override/classes, pasted all from tutorial but...... my website won't load anymore...
am i doing wrong something?