We're currently beta testing a new update to the Steam websites that uses a responsive design to provide a better experience on mobile phones, tablets, touch-enabled laptops, and other devices.
You can see the beta by visiting
http://steamcommunity.com in your browser on your mobile phone or tablet. These changes will be coming to the Steam Mobile App in a future update.
Currently the following parts of the Steam Community are included in the beta:
Profile and most sub-pages, including badges, trading cards, games list, achievements, wishlist, screenshots, workshop contributions, comment notifications, reviews, and more
The Friend Activity feed
The Community Activity page (home page), game hubs, forums, and guides
Groups
Discussions