In CSS, setting an element’s background color and changing text font size can be achieved by combining two properties: background-color is used to set the background color, while font-size is used to set the font size. Here’s a simple CSS code example showing how to set these two properties simultaneously:

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.element {
  background-color: #ff0000; /* Set background color to red */
  font-size: 20px; /* Set font size to 20 pixels */
}

In this example, .element is a selector that specifies which HTML element these styles should be applied to. The background-color property is used to set the element’s background color, which is set to red (#ff0000). The font-size property is used to set the size of the text within the element, which is set to 20 pixels.

By applying this CSS code to an HTML element, you can simultaneously change both the element’s background color and text font size.

There are multiple methods to achieve horizontal and vertical centering of elements in CSS. Here are several commonly used techniques:

1. Using Flexbox (Flexible Box Layout):

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   .parent { display: flex; justify-content: center; /* horizontal centering */ align-items: center; /* vertical centering */ }

2. Using Grid (Grid Layout):

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   .parent { display: grid; place-items: center; /* achieves both horizontal and vertical centering */ }

3. Using Absolute Positioning:

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   .parent { position: relative; } .child { position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); /* offset by 50% to achieve centering */ }

4. Using Table Layout:

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   .parent { display: table; width: 100%; height: 100%; } .child { display: table-cell; text-align: center; /* horizontal centering */ vertical-align: middle; /* vertical centering */ }

5. Using Inline Block and Text Alignment:

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   .parent { text-align: center; } .child { display: inline-block; vertical-align: middle; text-align: center; }

Each method has its own use cases, and you can choose the most appropriate one based on your specific layout requirements.