An increasingly split internet, or 'splinternet', of connected devices requires much more advanced website development from businesses, Forrester has warned.
Speaking as the analyst house launched the Forrester Forum in Barcelona today, Stephen Powers, principal analyst at the firm, said traditional PC-based internet experiences were "waning".
"Instead, customers are engaging with you through smartphones, tablets, and even Internet-connected TVs on the browser of their choice," he said.
"Marketing is already wrestling with this customer 'splinternet', and content and collaboration professionals face a confusing array of technologies to support it - mobile experiences in particular."
He added: "Many people are engaged on at least two different channels, and firms have to be able to deliver this."
Businesses faced difficult choices on tablet and phone internet delivery, such as whether to provide mobile websites or applications as the preferred route.
Some of the industries that are best addressing this are "retail and travel", according to Powers, because they are "often at the forefront of change when it comes to customer service".
More traditionally-minded businesses, including in the financial industry, were sometimes slower to adapt to change, he said.
"If you don't research what will work best for your organisation, and then take action, you could deliver a bad customer experience," he said.