You can check them in the following ways.
How to check the appearance from the Web browser version to the mobile browser version
On a PC, you can check the appearance of the mobile browser version by reducing the width of the browser display.
How to check the appearance from the mobile browser version to the Web browser version
Rotate the display of the mobile device to horizontal, and reduce the zoom level of the browser to around 50%* (※) to check the appearance of the Web browser version.
※The zoom level at which the Web browser version display switches may vary depending on the device.
Related: How to View Manuals (Web Browser Version)
https://teachme.jp/8/manuals/42394904
Related: How to View Manuals (Mobile Browser)
https://teachme.jp/8/manuals/42393521