There are two ways to present mathematical expressions on web pages now, i.e. as an image or installing plug-ins on web browser. To make up the shortage of both methods, a web mathematical equation editor named E-Math is presented. E-Math is based on Content MathML and implemented in JavaScript and XSLT, and therefore supports further numerical and symbolic computation online. Furthermore, the source code of E-Math is openly available. This paper provides E-Math’s framework and a technical solution.