This page describes the exam:
http://www.microsoft.com/learning/en-us/exam.aspx?id=70-515
Notice a section titled "Skills Measured." This is the exam syllabus.
Also, in the section "overview", you will notice a part labelled "Credit Toward Certification." This will tell you which certifications make use of this exam. The values of the certifications themselves are argued in the "Certification Benefits page":
http://www.microsoft.com/learning/en-us/certification-benefits.aspx
Note, however, that 70-515 deals with version 4.0 of the Framework, which has alredy been superseded by version 4.5. You may consider to pursue instead a certification on the latest version:
http://www.microsoft.com/learning/en-us/mcsd-web-apps-certification.aspx