To insert an image as the background in CSS, you can use the background-image property. Here's an example of how to do it:

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body {
  background-image: url("image.jpg");
  background-repeat: no-repeat;
  background-size: cover;
  background-position: center;
}

In the example above, image.jpg should be replaced with the actual path or URL of the image you want to use.

The background-image property sets the image to be used as the background, while background-repeat: no-repeat ensures that the image is not repeated. background-size: cover makes the image cover the entire background area, and background-position: center centers the image within the background.

You can adjust these properties according to your specific requirements.

To change the orientation of a background image in CSS, you can use the background-position property. This property sets the initial position of the image. You can set the position by providing two values; the first value controls left/right position, and the second value controls up/down position.

For example, if you want to move the background image to the right and center it vertically, you can use the following code:

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background-position: right center;

This would move the background image to the right side of the container and center it vertically.

You can adjust the values to move the background image in different directions and positions. Here is a link to an example of using background-position in CSS: CSS Background-position

To animate a group of images, you can use a combination of HTML, CSS, and JavaScript. One way to do this is by using CSS Sprites and the @keyframes rule in CSS to create the animation.

Here's an example code snippet (using HTML, CSS, and JavaScript) that animates a group of images:

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<div class="animation"></div>

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.animation {
  width: 100px;
  height: 100px;
  background: url(images-sprite.png) left top;
  animation: play-sprite 0.8s steps(4) infinite;
}

@keyframes play-sprite {
  100% { background-position: -400px; }
}

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// Since we set the number of steps to 4, 
// we need to have 4 images in our sprite.
// Each image has a width of 100px, so the
// sprite's width is 4 times that: 400px.

var spriteWidth = 400;
var steps = 4;

// When the animation starts, we need to know
// the current step (or image) and position the
// sprite accordingly.

var currentStep = 0;
var currentPos = 0;
var speed = 100;

function animate() {
  currentStep = (currentStep + 1) % steps;
  currentPos = (-currentStep * spriteWidth) + 'px';
  document.querySelector('.animation').style.backgroundPosition = currentPos + ' top';
}

setInterval(animate, speed);

In this example, we first create a div element with a class of .animation. We then set the background property of this element to a sprite image called images-sprite.png and position it to the left and top of the element.

Next, we define a @keyframes animation rule called play-sprite that plays the sprite animation indefinitely.

In the JavaScript code, we calculate the width of the sprite and the number of steps (or images) it contains. We then set up a loop that runs every speed milliseconds and updates the background-position of the .animation element to show the next image in the sprite sequence.

This is just one way to animate a group of images using HTML, CSS, and JavaScript. There are many other techniques and libraries available, depending on the specific requirements of your project.

To set a full page background in CSS, use the background-size and background-position properties. When background-size is set to cover, it will scale the image to cover the entire container. You can then control the vertical alignment of the image using the background-position property. The syntax is background-position: horizontal-position vertical-position;.

For example:

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body {
    background-image: url("background-file.jpg");
    background-size: cover;
    background-position: center top;   
}

You can use the background-image CSS property to add a background image from a local file to an element (in this case the body):

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body { 
  background-image: url('./my-background-image.jpg');
}

You will also need to set the background-size, background-repeat, background-attachment, background-position and background-origin properties appropriately based on the style you wish to achieve.

For more information, please see MDN Documentation on the background-image CSS property.

To fix a background image, you can use the CSS background-image property. To set the background of an element, use a basic syntax combining the background-image property and the url() function. See the example below:

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element {
    background-image: url("image.jpg");
}

You can also set the size, position, and tiling option of the background image with the background-size, background-position, and background-repeat properties. See the example below:

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element {
    background-image: url("image.jpg");
    background-size: cover; // makes background image full-coverage
    background-position: center;
    background-repeat: no-repeat; // removes any tiling that would otherwise occur
}

For more information about the CSS background-image property and how to use it, you can refer to MDN's documentation.