Mobile UX: 7 mistakes that lose 30% conversion

Mobile accounts for 62% of web traffic in the UK. Most business websites were designed on a 27-inch monitor. The gap between "looks fine on desktop" and "actually works on mobile" is where revenue disappears.

We audited 80 SMB websites in 2025. These 7 mistakes appeared in 70%+ of them.

1. Touch targets under 44px

Apple's HIG specifies 44×44pt minimum. Google recommends 48×48dp. Most "mobile-responsive" sites have nav links, form checkboxes and icon buttons at 20–28px. On a phone screen with a thumb, you miss every other tap. Fix: audit every clickable element on mobile. Anything under 44px gets bigger.

2. Full-width hero video on mobile

That beautiful 30MB background video auto-plays on 4G, drains battery, and adds 4 seconds to load time. Most users are gone by second 3. Fix: use a static image on mobile, video only on desktop (CSS media query + lazy load).

3. Horizontal scroll on forms

Input fields set to a fixed width wider than the viewport. The user tries to type their email, the field scrolls off screen. 60% abandon the form at that point. Fix: all form inputs width: 100% with appropriate max-width on larger screens.

4. Font size under 16px

iOS zooms in automatically when an input field has a font size under 16px. This breaks the entire layout and disorients the user. Fix: minimum 16px on all input elements. Body text should be 16–18px on mobile.

5. The "above the fold" CTA is invisible on mobile

The desktop design has a hero with a CTA button. On mobile the hero takes up 90% of the screen and the button is below the fold. Users scroll expecting content, hit nothing, and leave. Fix: test every hero section on a 390px viewport. The CTA must be visible without scrolling.

6. Pop-ups on mobile

Google penalises intrusive interstitials on mobile since 2017. A full-screen newsletter pop-up on mobile is both a UX disaster and an SEO penalty. Fix: if you must have a pop-up, trigger it at 80% scroll depth, not on page load. And give users a real close button.

7. No sticky contact method

On desktop, the phone number is in the header. On mobile, the header is compressed. The user wants to call you and cannot find the number without scrolling back to the top. Fix: sticky CTA bar at the bottom of mobile screens. "Call" and "WhatsApp" buttons. 3mm of screen space, enormous conversion impact.