The size of the horizontal menu bar of a website is generally 30px, 50px or 60px, depending on your needs. The size of the menu bar at the top of the site. You can look at the size of menu bars on other websites and have as many as you want. At present, the size of ios is _@2x. Besides plus, you need to pay attention to the navigation bar 60PX and the bottom tab bar 148PX, and the size needs _@3X, which is 1.5 times.