Fix spelling of architectures

Author: nurmukhametov

index.html

@@ -73,7 +73,7 @@ <h1>Overview</h1>
         <p><tt>ispc</tt> compiles a C-based SPMD programming language to
           run on the SIMD units of CPUs and GPUs; it frequently provides 
           a 3x or more speedup on architectures with 4-wide vector SSE units
-          and 5x-6x on archituctures with 8-wide AVX vector units, without 
+          and 5x-6x on architectures with 8-wide AVX vector units, without 
           any of the difficulty of writing intrinsics code.  Parallelization
           across multiple cores is also supported by <tt>ispc</tt>, making it
           possible to write programs that achieve performance improvement