Slicing

Slicing is the process of dividing a single 2D user interface composition layout, into multiple image files of the graphical user interface for one or more electronic pages.
Slicing is used in many cases where a graphic design layout must be implemented as interactive media content.
 Slicing reduces work loads and computer data storage space requirements to needing only the part of a  image that changes instead of the whole image. On the web, slicing breaks up one large image into many smaller ones, which reduces "page weight" or load time considerably.

We can achieve slicing within html by using the <div> tag.
Here is a example:

<div style="color:#0000FF">
  <h3>This is a heading</h3>
  <p>This is a paragraph.</p>
</div>

 

This will place my heading and paragraph within a div, (an invisible box) which then can be manipulated in CSS, size, height, margins.