A two-key scheme for concealed embedding of data in open source HTML pages is proposed. The first key is used to encrypt the embedded message. The second key is required to encode the hidden message. The body structure of a web page is a tag tree. The embedding algorithm uses class tags. Empty classes do not affect the display of a web page in a browser. Hidden data is encoded by adding new vertices to the tag tree. New vertices are added to the leaf vertices of the page that serves as the container. There are leaf vertices that exclude the addition of empty classes to them. Each tag encodes eight bits of hidden information. The embed key is used to form class names that include new tags. Class names are disguised as the framework used on the web page. Names are generated using a hash function and an embedding key. The message extraction algorithm is based on knowledge of embedding and encryption keys by the receiving subscriber. The algorithm for extracting data boils down to searching for tags by their names and then decoding them. The developed algorithm can be used for transmitting hidden messages on the Internet. The proposed algorithm is open. Resistance is ensured by the secrecy of encryption and embedding keys. Direct enumeration is necessary to hack the system if the tag embedding key is unknown. The algorithm for forming class names does not violate the statistical patterns of the legal class names set. Resistance is provided by the key retention policy. The average throughput of the algorithm is 0,003 bits per byte.