Updated docs

docs/docs/ml.xml

@@ -31,7 +31,8 @@
             programming approach using C++ templates. In particular, each algorithm is parameterized
             to allow a user to supply either one of the predefined dlib kernels (e.g. <a 
             href="#radial_basis_kernel">RBF</a> operating
-            on <a href="containers.html#matrix">column vectors</a>), or a new user defined kernel. 
+            on <a href="containers.html#matrix">column vectors</a>), or a new 
+            <a href="using_custom_kernels_ex.cpp.html">user defined kernel</a>. 
             Moreover, the implementations of the algorithms are totally separated from the data on 
             which they operate. This makes the dlib implementation generic enough to operate on 
             any kind of data, be it column vectors, images, or some other form of structured data.