The concept of material honesty comes from architecture. It suggests that we should design or build things using materials in an honest way: Either use brick, or flat plaster, but do not dress up plaster to look like brick. It's not true to the material you're using.
Material honesty applies to the web, too. The materials of the web are HTML, CSS, and images. Using those materials honestly means building with them in the way that they intend to be built.
Kevin Goldman tells us that the web wants itself to be flat, and without decoration:
Without all the shading, shadows, and bulbous buttons, we get a flatter (or honest, or native, or authentically digital) web. Call it what you will, the flat web focuses more on content. It's quick to craft. It loads quickly, too. Designer and developer workflow is more collaborative because both use the same tools. Talented “flatlanders” add emotional depth to their work, but it's not the kind that wows on Dribbble ... The palette of emotional design for flatlanders is instead temporal. Temporal beauty lives in state-change animations, nuanced timing effects, strategically placed user feedback, and other “interesting moments,” not drop shadows and Photoshop layer effects. Flatlanders build all kinds of emotion and depth combining these moments with delightful microcopy, personality, and typography. All honest—all web—all good ... Again and again, design history shows that when we try to trick a viewer into believing a material is something it's not, the value and the timelessness of the design decrease.
Frank Chimero talks about "following the grain of the web" when doing work for his clients. Doing that makes the work easier, and the result more resilient.
Easy to implement → ← Timeless Back to the table of contents
Directness is best in my experience, so a great photo, memorable illustration, or pitch-perfect sentence does most of the work. Beyond that, fancy implementation has never moved the needle much for my clients. My web design philosophy is no razzle-dazzle. My job is to help my clients identify and express the one or two uniquely true things about their project or company, then enhance it through a memorable design with a light touch ... In the past, I've called this following the grain of the web, which is to use design choices that swing with what HTML, CSS, and screens make easy, flexible, and resilient ... It seems there are fewer and fewer notable websites built with this approach each year. So, I thought it would be useful to remind everyone that the easiest and cheapest strategy for dealing with complexity is not to invent something to manage it, but to avoid the complexity altogether with a more clever plan.