The best banner size is the one that fits a real, visible position on your website without burying the content. For ShowMeYours, the supported formats are 300 × 250, 728 × 90 and 320 × 100. Each has a different visual job. Treating them as interchangeable leads to poor creative and awkward layouts.
What each dimension means
The numbers describe width by height in CSS pixels for the intended display slot. A 300 × 250 medium rectangle is relatively deep, a 728 × 90 leaderboard is wide and shallow, and a 320 × 100 banner is optimized for narrow mobile layouts. The creative file and placement should agree on the intended format.
300 × 250: flexible for content-adjacent layouts
A medium rectangle can sit beside an article, after a group of cards or within a spacious content grid. Its height makes it easier to combine branding and a simple message. On narrow screens, put it in the normal document flow instead of forcing a sidebar beside a video player.
Avoid inserting the rectangle in a way that causes unexpected layout movement. Reserve the slot’s height before the creative loads. If the ad is not requested or cannot be filled, your layout should still behave predictably.
728 × 90: useful on desktop, awkward on small screens
The classic leaderboard works when the page has enough horizontal space. It can complement a site header or a content transition, but it should not displace the primary navigation or push the first useful content too far down. On a phone, a fixed 728-pixel slot often overflows the viewport.
Don’t shrink it to 320 pixels and call it a mobile format: the text and controls become difficult to read. Supply a distinct 320 × 100 creative and choose the appropriate size at the correct breakpoint.
320 × 100: prioritize mobile clarity
This banner gives more vertical space than a thin strip but far less room than a medium rectangle. The safest approach is large readable copy, a small logo and one visual or action. On a 320-pixel viewport, allow the slot to fit the available page width without causing horizontal scrolling.
Practical layout recommendations
| Context | Candidate format | What to check |
|---|---|---|
| Desktop article or listing between sections | 728 × 90 | Fits container; does not obscure navigation |
| Wide desktop sidebar or in-feed block | 300 × 250 | Actually visible; not squeezed |
| Mobile feed or article break | 320 × 100 | No horizontal overflow; readable copy |
| Mobile article between blocks | 300 × 250 | Fits the viewport and content rhythm |
These are design recommendations, not a claim that a particular position always earns a higher conversion rate. Audience behavior, device mix, surrounding content and campaign quality matter.
How responsive selection should work
A responsive layout can choose a desktop slot for sufficiently wide viewports and a mobile slot for narrow ones. That selection must follow the advertising network’s integration instructions. Avoid requesting both sizes invisibly and counting both as exposure. An impression should represent a legitimate rendered ad opportunity, not simply a hidden element on the page.
If you embed JavaScript, use the domain-specific ShowMeYours code issued for your site. Do not hard-code a neighboring publisher’s key, alter validation callbacks or assume that setting a large CSS width is the same as using a supported format. Our WordPress installation guide explains the safe workflow.
Design templates: what belongs in the creative?
For 300 × 250, consider brand + benefit + one action, arranged vertically. For 728 × 90, place the benefit and brand on a single readable line with a concise action. For 320 × 100, remove all secondary copy and keep only what is essential.
Export at native dimensions and compare at actual size. The goal is not to fit the most words but to be understood in a glance.
Accessibility, performance and trust
Do not disguise ads as navigation buttons. Give the site visitor an honest way to distinguish paid or exchanged advertising from site content. If you are rendering an image ad yourself, add useful alternative text appropriate to the creative; avoid misleading generic descriptions. Lazy loading can improve performance, but ad loading and impression validation must follow the exchange’s implementation instructions.
Frequently asked questions
Can I run only one supported size?
The available inventory and integration rules determine that. If your site only has one suitable location, start there rather than damaging the layout to display three different units.
Does 728 × 90 always outperform 300 × 250?
No. It occupies a different visual position and usually reaches a different audience context. Compare real campaign engagement instead of assuming that bigger width means better results.
Should I load an offscreen banner?
Follow the network’s current instructions and avoid creating fake or hidden impressions. An ad request is not equivalent to a valid viewable impression.
Related guides: design a readable creative and choose where it belongs on your page.