I’m a beginner trying to build a personal blog-type website, and I used someone else’s guide html, but I can’t figure out how to change the background image. They had their background image as a square tile repeating, which I thought was nice, but I wanted a different picture so I replaced their image link with an imgbb link where I uploaded my picture but it hasn’t been working.
Their background image text was also written weird, so I changed it a bit, but it still won’t work, and this other section of the code higher up has this error that I don’t understand (the image). Any help on what this means is greatly appreciated, I’m very new to this T_T
enter image description here
this second image is my background image (and header) code

I tried looking up the error name and couldn’t find anything, and moved some of the wording/colons/etc stuff around to see if it would fix it.