Can I apply both position: relative and float: left on one element? Like this:
div {
float: left;
position: relative;
top: 0px;
Yes, You can use both.
You will use float:left to position element to left side and permit next element to position right side of this.
position:relative will affect itself and it's children, to take own position. when you will use left:npx;top:npx it will move this element left,right,top and bottom.
You can check this demo: jsfiddle link