One size does NOT fit all. Your website needs to look good on all devices.
In December 2012, the mobile share of web traffic across the world was 14.55% compared to 8.04% a year before. In the US, 25% of all web traffic comes from mobile-only users, while in developing countries like Egypt these numbers go up to 70%. If the growth rate continues like that, we can expect mobile internet to take over desktop internet usage by 2014.
There is no way around facing this rapid change. More even, we would do good embracing it so we can adapt early and ensure a steady experience for our users — now and in the future. As mobile internet usage increases, so do the expectations users have towards your website. We design web sites with this in mind.