CSS: Add top margin to future portfolio projects

It won't add the margin to the first two projects, only those coming
after them. This is the CSS2 way instead of the CSS3 :not selector way
just in case for better browser compatibility.
diff --git a/css/style.css b/css/style.css
index 67af2df..d4347b0 100644
--- a/css/style.css
+++ b/css/style.css
@@ -239,7 +239,8 @@
       margin-top: 20%; } }
   @media screen and (min-width: 1200px) {
     .portfolio-projects--title {
-      margin-top: 5%; } }
+      margin-top: 5%; }
+    .portfolio-projects .col-lg-6 + .col-lg-6 + .col-lg-6 {margin-top:40px} }
 @media screen and (min-width: 768px) {
   .portfolio-projects--desc {
     margin-top: 10%;