css box-sizing
/* Always keep this code inside your css file*/
*{
box-sizing: border-box;
}
.div-1{
/* width: 100%; Default - Block Element*/
padding: 10px;
box-sizing: border-box;
/*
content-box is default for box-sizing
content-box will remove border-box effect.
*/
}
/*
after applying padding [border also will increase the width]
10px added to left and right from padding
the .div-1 width is now 100% + 20px, and that may cause errors in your layout
according to your work.
to solve the problem and force the width to be as i give to it
we use box-sizing => our div width will not be affected by padding or border
*/