The body
element has some margins by default. Unless you remove them, any element that you put inside, no matter it’s width (unless it’s in position absolute
I think) will have some borders. They aren’t borders, but the gab in between the end of your element and the side of the body. Try this :
body{
margin: 0;
}
If that doesn’t work, then please show us an example of your code on JSBin, Codepen or similar (or even a live version if possible).