FileInfo.com - The File Extensions Resource

.RHTML File Extension

File Type	Ruby HTML Web Page
File Format	File
Common?	No
File Description	Web page containing Ruby code or scripts; processed on a Web server running Ruby on Rails before the page is sent to the Web browser
Program(s) that open rhtml files	Mac / Windows: Any Web browser

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/rhtml