how to set the width of a element to the width of the page css code example

Example 1: css image size adjust

squareImage {
  border: 1px solid #ddd;	/* thickness and color of border */
  border-radius: 4px;		/* edge rounding of border */
  width: 150px;				/* width of image (px or % or auto) */
  height: auto;				/* height of image (px or % or auto) */
}

Example 2: how to make a workspace container bigger in css

#workspace_container {
        height: 1000px;
		width: 83%;
		min-width: 1060px;
    }

    #workspace {
        padding: 10px;
        /*height: 590px; */ /* (height of activity_area) - (2*padding) - (height of controls) */
        height: 1000px;
    }