Custom CSS to make Background transparent ignored until the page is reloaded! Help!

https://bamboo-circle-erbl.squarespace.com/projects

The white background behind the gallery should be transparent. I have placed the appropriate code in order for the background to be transparent, however it remains opaque white upon first loading the page. If one RELOADS the page, the custom css take hold. Why do browsers ignore my custom css upon first load only to reject it in favor of custom css upon reload? Help me Obi Wan Kenobi, you're my only help.  

I suspect you have inserted the css into the page / section injection point. 

Instead, move it to sitewide custom css area - Design > Custom CSS

NB. You don’t need <style > .. </style > in the custom css area