How Website Design Affects Conversions

Most design debate is about taste. A smaller set of decisions genuinely changes whether people get in touch, and they are not usually the ones being argued about.

What actually matters

Visual hierarchy

Can someone scanning the page in three seconds find the most important thing?

Hierarchy is created by size, weight, spacing and contrast — not by colour alone. If everything is emphasised, nothing is, and the reader has to do the work of deciding what matters. Many will not.

Readability

• Line length. Roughly 60–75 characters. Full-width paragraphs on a desktop are genuinely hard to read.
• Line height. Around 1.6–1.75 for body text. Tight leading looks designed and reads badly.
• Font size. 16px minimum for body. 14px body text is a decision made by someone with good eyesight on a large monitor.
• Contrast. WCAG AA minimum. Light grey on white is the single most common accessibility failure on business sites, and it fails for everyone in bright light, not just people with impaired vision.

The next step being findable

The primary action should be visually obvious without being obnoxious. If a visitor has to hunt for how to contact you, some proportion will not.

Mobile behaviour

Most traffic is mobile and most design review happens on a desktop. Tap targets large enough, no horizontal scroll, forms that work with a phone keyboard, and nothing important hidden behind a hover state — because there is no hover on a touchscreen.

Load behaviour

Not speed exactly, but what happens while loading. Content that jumps as images arrive, or text that flashes in a fallback font and then reflows, undermines confidence before anyone has read a word.

What mostly does not matter

• Exact brand colour, as long as contrast is adequate
• Font personality, as long as it is readable
• Whether it looks current, within reason — dated and clear beats fashionable and confusing
• Animation, which occasionally helps comprehension and more often delays it
• Whether it resembles a competitor

Things that actively hurt

Carousels. People rarely see past the first slide, and they push real content down.

Autoplaying video with sound. Universally disliked.

Popups on arrival. Interrupting someone before they know what the site is costs more than the email address gains.

Hover-only navigation. No hover on touch. If a menu only opens on hover, mobile users cannot reach it — and neither can a crawler, which is a separate and equally expensive problem.

Text over busy images. Almost always fails contrast somewhere.

Infinite scroll on a site with a footer. The footer becomes unreachable.

The relationship with accessibility

Accessible design and converting design overlap heavily. Sufficient contrast, clear hierarchy, real focus states, labelled form fields, sensible heading order — all of these help everyone, and several of them are legal requirements in the UK for many organisations.

A site that is hard to use with a keyboard is usually also hard to use in a hurry.

How to tell if a design change worked

Record a baseline. Change one thing. Wait long enough to have meaningful data.

At low traffic volumes you will not get statistical significance, and pretending otherwise is worse than admitting the evidence is directional. Directional evidence plus a clear rationale is a legitimate way to make decisions at small scale.