Creating a diagonal line/section/border with CSS

Question

I am trying to create a diagonal line on a webpage, to act as a section/section break. This is essentially a split colour section. I cant use an image as if the page gets en

Answer 1

You can do this without any clipping and just using borders in a unique way. This should also be cross-browser compatible, but I haven't tested it across everything

Initially divided this into 2 separate divs / triangles and joined them, but thanks to web-tiki and kaiido perfected it to use only 1 div and minimal CSS

*{
  border: 0;
  padding: 0;
  margin: 0;
}

#gradient {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 90px 100vw 0 0;
  border-color: yellow black transparent transparent;
  transform: scale(1.0001);
}

Original Answer using multiple divs:

*{
  border: 0;
  padding: 0;
  margin: 0;
}

#container {
  width: 100%;
  position: relative;
}

#container div {
  position: absolute;
}

#top-triangle {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 90px 100vw 0 0;
  border-color: yellow transparent transparent transparent;
}

#bottom-triangle {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 0 0 90px 100vw;
  border-color: transparent transparent black transparent;
}