It’s 2018, more than half of your website traffic probably comes from mobiles. If your website is not responsive yet then upgrade it fast. A responsive website is that which was designed to adjust its design based on the device screen size. Yes. They are more difficult to design since you have to test it in both small screens and big screens, but it’s worth it. If your landing pages are not responsive go fix them right now, this will help you with your digital marketing efforts as well, since google loves pages optimized for mobile devices.