write an html/css code to align image vertically in a division that spans vertically on the whole webpage

Sure, here's an example HTML/CSS code to align an image vertically in a division that spans vertically on the whole webpage:

HTML code:

<div class="container">
  <div class="vert-center">
    <img src="your-image-url-here" alt="Your Image" />
  </div>
</div>

CSS code:

.container {
  height: 100vh; /* sets the height to the full height of the viewport */
  display: flex;
  justify-content: center;
  align-items: center;
}

.vert-center {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-direction: column;
}

In this example, we use the `height` property to set the height of the container to the full height of the viewport using the `vh` unit. We then use `display: flex` and `justify-content: center` and `align-items: center` to center the child elements both horizontally and vertically within the container.

To align the image vertically, we wrap it in an additional `div` element with the `vert-center` class. We then use `display: flex` and `justify-content: center` and `align-items: center` with `flex-direction: column` to center the image both horizontally and vertically within this inner div.

You can adjust the image size and other styles as needed to fit your specific requirements.