css in clearfix results nothing below header seen NSFW

Hi,

Link to my website NSFW

I have been trying to use code for 'tabs with only css without jquery'.
On inserting css in clearfix the post did not upload.
Now none of the posts show anything below header.

I tried similar thing in twentyfourteenchild, broke the site and got white screen, but didn't learn.

I'm sure your expertise will enable me to resolve this so that I get back my website
and hopefully I manage to get tab function in posts as well.

Thanks in advance,
Dr. Ashok