High risk HTML compression is a feature that condenses the HTML file for faster speed. When the HTML compresses, W3C validation is canceled and the compatibility on all browsers may suffer. To keep W3C validation on without compressing the HTML files, enable "Keep W3C validation" in the back office. This feature is dependent on the each user's preference. PrestaShop allows you to have High risk HTML compression is a feature that condenses the HTML file for faster speed. When the HTML compresses, W3C validation is canceled and the compatibility on all browsers may suffer. To keep W3C validation on without compressing the HTML files, enable "Keep W3C validation" in the back office. This feature is dependent on the each user's preference. PrestaShop allows you to have the option to choose.