Websites with inappropriate representation of images (mostly on mobile) force a user to close them before the browser even finished loading the remaining content. They let one wait longer, pay for additional traffic and they destroy the website's design. Nowadays internet users consume information on multiple devices with different screen resolutions, so they attach a great importance to the ability to surf a web page equally good on different screen sizes.
As of iOS8 its imposible to add a third-party dictionary to a non-jailbroken iOS. Apple permits the user only to download a dictionary from their registry. Currently there is only one approach to add the custom dictionary — by replacing the content of the existing one, which was previously downloaded from Apple registry.