Hi Matt 

sorry for the late response (teaching has been extra painful this year.. :))

i tried to use what you suggested but couldn't get the expected results, but im sure im doing things wrong :D

so i created a file named

 /home/zeltak/org/files/Uni/Courses/css/left.aligned.css

in it i have pasted this

.left p, .left ul, .left li {
text-align:left;
}

now in my org file i have these added lines on the top

#+REVEAL_EXTRA_CSS: /home/zeltak/org/files/Uni/Courses/css/left.aligned.css
#+ATTR_HTML: :class left

i also tried adding the #+ATTR_HTML: :class left under specific headers

in both cases the text is still centered, any clue? i must be doing something horribly wrong right :) ?

thx

Z