CSS is Cascading Style Sheets, the language used to control the visual presentation of HTML content. In web development, this term gives marketers, designers, developers, and business owners a precise way to talk about work that affects visibility, user experience, measurement, and revenue.
In practical web development work, the important question is not just what CSS means, but how it should influence decisions. It matters because development decisions affect speed, security, scalability, tracking, SEO, and maintenance. A site that looks good but is fragile or hard to update can quietly hold back every marketing channel.
A strong approach should connect CSS to measurable outcomes such as qualified traffic, calls, form submissions, booked appointments, ecommerce revenue, or lower acquisition costs.
Example
On a WordPress or Shopify build, css might affect how the site is coded, hosted, secured, updated, or connected to third-party tools. For example, a lead-generation website may need reliable form handling, fast page loads, SSL, tracking tags, backups, and a staging environment before launch.