Borders and border radius

A border surrounds an element's content and padding. The border shorthand commonly lists width, style, and color. border-radius rounds the corners. A border normally stays invisible if no border style is supplied.

Read a rule first

A CSS declaration uses property: value;. The semicolon ends one declaration, and braces group declarations for the same selector. The browser reads rules from top to bottom. When several rules match one element, the cascade considers their source, selector specificity, and order.

<div class="card">A simple card</div>

.card {
  padding: 20px;
  border: 2px solid #0f766e;
  border-radius: 8px;
}

Change one value at a time and watch the text, color, size, or position. This connects each declaration to a visible result. Browser developer tools show the result of the same matching process.

A useful checking order

• Confirm that the selector matches the intended HTML element.
• Check the property name, colon, value, and semicolon.
• Test narrow space, longer text, and keyboard use.

<div class="card">A simple card</div>

.card {
  padding: 20px;
  border: 2px solid #0f766e;
  border-radius: 8px;
}

A common source of confusion

CSS changes presentation and layout; it does not change the meaning of the HTML. Keep meaningful HTML elements and style them, rather than choosing the wrong element only for its default appearance. Readability comes before decoration.

<div class="card">A simple card</div>