QR code component

The CSS code you provided sets styles for the body element, which is the top-level container for the content of an HTML document. Let's break down the behavior step by step:

1. background-color: yellow;

   • This line sets the background color of the entire body element to yellow.

2. width: 300px;

   • This line sets the width of the body element to 300 pixels. This means the body will be 300 pixels wide.

3. border: 1px solid red;

   • This line sets a 1-pixel solid red border around the body element.

Now, let's understand why you see a small rectangle:

• The background-color property sets the background color of the entire body, filling the viewport area with yellow. This makes the entire background yellow.

• The width property sets the width of the body, but it doesn't affect the background color. It only affects the width of the content inside the body.

• The border property adds a 1-pixel solid red border around the body. Since the width of the body is set to 300 pixels, the border is applied around that width.

So, you see a small red rectangle because of the border around the body. The border is applied to the outer edge of the body element, creating a 300-pixel-wide red rectangle around the yellow background.

The part outside this red rectangle represents the space outside the body element, which is usually considered the margin area. In this case, the margin area is not visible because it's the viewport area, and it is filled with the yellow background color as specified by the background-color property. However, if you had content inside the body, it would be contained within the 300-pixel-wide red-bordered box, and the margin area outside that box would remain yellow.

I think this is the answer you are looking for:

In HTML and CSS, the body element, by default, takes up the entire height of the viewport, even if its content has zero or minimal height. This behavior is a result of the default styles applied by browsers.

Here's why the body background color fills the whole screen even if it has zero height:

Default Styles: Browsers have default styles for HTML elements, including the body. By default, the body element has a margin of 8px, which can create spacing around the body content. Additionally, the body has default padding and border values set to 0.

Collapsing Margins: In CSS, margins of adjacent elements can sometimes "collapse" into each other, causing the effective margin to be larger. If there is no content or explicit padding or margin set on the body, the margin might collapse to the html element, causing the body to extend to the top of the viewport.

Viewport Height: The body element is expected to fill the entire viewport by default. If it has no content or minimal content with no explicit height, it will still expand to occupy the full height of the viewport.

To prevent this behavior and make the body element take only as much height as its content, you can explicitly set the height of the body to auto in your CSS:

body { height: auto; /* Other styles */ } Or, if you want to ensure the body element only takes the height of its content and has no margin, you can use:

body { margin: 0; height: auto; /* Other styles */ }

By setting height to auto, you instruct the browser to adjust the height of the body based on its content, and by setting margin to 0, you remove any default margin that might be collapsing with other elements.