In some web applications there are fields and each field has its syntax. Usually that syntax is described with regular expressions. Programmers use them to instruct computer which input is correct and which is not. If the input is incorrect a user would like to know why it is wrong. One solution could be just to present the regular expression. Unfortunately many users are IT-laymen and they can not read regular expressions. Another solution would be to write a section in a user manual explaining which input is syntactically correct and which is not. Regrettably, that is a time consuming process. Thus, a question arises, if such a description could be generated automatically. The paper presents an experimental system that automatically generates an explanation of a given regular expression. This paper focuses on problem of generating syntax diagrams from regular expressions.