Fix spelling mistake in Lesson 2.

docs/index.html

@@ -325,7 +325,7 @@ <h4>Proper program exit</h4>
 
                         <h5>Some more background</h5>
 
-                        <p>After successfully learning now to execute a system call in Lesson 1 we now need to learn about one of the most important system calls in the kernel, sys_exit.</p>
+                        <p>After successfully learning how to execute a system call in Lesson 1 we now need to learn about one of the most important system calls in the kernel, sys_exit.</p>
 
                         <p>Notice how after our 'Hello, world!' program ran we got a Segmentation fault? Well, computer programs can be thought of as a long strip of instructions that are loaded into memory and divided up into sections (or segments). This general pool of memory is shared between all programs and can be used to store variables, instructions, other programs or anything really. Each segment is given an address so that information stored in that section can be found later.</p>