revisiting this old thread as still have this issue, Line 1 has this
<!DOCTYPE html>
then i get 170 empty lines before i get this code
<html id="XF" lang="en-US" dir="LTR"
style="font-size: 62.5%;"
data-app="public"
data-template="forum_list"
data-container-key=""
data-content-key=""
It annoys the pedant in me and might possibly be getting Google to ever so slightly penalise my site perhaps. How could i find what is causing it ?