Ah yes, that SEPR does have an ad block with background color #FDF6E5. However, that color is only 10% yellow. Objectively, that should present a very faint yellow.
If you're seeing a gold-ish yellow background, then your monitor is set to low brightness or Gamma 2.2. That way, you won't see colors as they are.
My monitor is set for accurate colour representation. Gamma 2.2 is the norm these days and is what websites, photography software, video software all want these days.
Mac OS X used to be the lone hold-out at 1.8 gamma but those days are long gone. (Snow Leopard changed the default to 2.2 to be in-line with the rest of the industry). Windows has always been at 2.2 gamma.
If you're seeing a gold-ish yellow background, then your monitor is set to low brightness or Gamma 2.2. That way, you won't see colors as they are.