Layer perpendicular to Browser

The layer is perpendicular to the browser, which has always been a headache for new friends. In fact, the solution is like this: first we need position: absolute; absolute positioning. For the layer positioning point, the method of using the negative value of the external patch margin is used. The negative value is the layer width and height divided by two. For example, the width of a layer is 400, and the height is 300. Set the absolute distance between the upper part and the left part to 50%. The value of margin-top is-150. The value of 'margin-left' is-200. In this way, we can write a style that is perpendicular to the browser.