The purpose of diploma is web browser comparison. We recognize the reason for web browsers and web standards development. We describe in details the main web standards and present their contribution to web operating and also their indirect contribution to the information technologies. This diploma shows how important are web standards and how different browsers implement them differently or even not at all. The main aim of diploma is comparison and testing of five most-used browsers in the world and in Slovenia. At first we take a look at how they are distributed and continue with their performance, especially their speed in page loading and usage of memory. Further we test browsers from a user point of view. We evaluate their safety and...