Different computers and devices, especially mobile devices such as iPhones or smaller laptops can have smaller screens in which case you may need to scroll the webpage to see the full webpage.
Please note that most browsers also support the ability to increase and decrease the size of the webpage on your screen which means that if you find the webpage too big or too small you can adjust the zoom level in your web browser as well. There are different methods to do this but a very common one that is supported in most web browsers is to hold down the Ctrl key on your keyboard and then using the middle mouse wheel to zoom in and out of the webpage.