Responsive web design is an up-and-coming web site design technique that many web and mobile web design experts say holds a lot of promise. A merchant can design a site once that adjusts to fit the size of the screen of the device making the page request. It’s a modular design, where modules are reordered to fit the size of a desktop computer, a tablet PC or a smartphone. And it saves having to optimize a site thrice.

With a massive wave of shoppers accessing its site via mobile devices, a small e-retailer of pet supplies has taken the leap, redesigning its e-commerce site for the first time in five years and choosing a responsive design route to automatically push into the mobile commerce realm.

“Our mobile audience has been growing by leaps and bounds,” says PupLife co-founder and CEO Leslie Hayes-Houtkooper. “Our customers are shopping for dog supplies from a variety of platforms: workstations, laptops, tablets and mobile phones. We want to deliver a great customer experience on all platforms. Our new responsive site design does exactly that. With the new site, we are making it easier for dog owners to shop from any device.”

Hayes-Houtkooper says 20% of traffic comes from mobile devices. “These numbers will only grow over time,” the CEO says, “so this design positions us well for the holiday months ahead.”

The redesign is meant to reinforce the company’s focus on design and ease of use, with a modern look that has plenty of lovable dog photos, large product pictures and abundant white space, PupLife.com says.

“Design is important. Usability is important,” says Hayes-Houtkooper. “Our customers want a modern site design, but also one that is easy to navigate and use, without distraction. This new design accomplishes that with ease.”

U.K. web design firm CleanThemes helped develop the site.