This is an example of an MSP script that displays a Mathematica Plot3D in an webpage.
<html>
<body>
<%Mathlet MSPJavaView[Plot3D[Sin[x*y],{x,0,10}, {y,0,10}]] %>
</body>
</html>
This example is very similar to one of the examples on this page: Plotting Graphics.
You can see the source of that page as well: Source of Plotting Graphics.