Practical Guide to CSS Positioning
CSS position is sometimes considered an advanced topic because it can do things that are somewhat unexpected. Well, don’t let “the experts” intimidate you from pursuing excellence in your CSS competence! It’s a very accessible topic once you’re equipped with some of the underlying ideas.
An important concept to understanding relative/absolute positioning is render flow.
The general idea is that HTML elements all take up some space. Your browser’s rendering engine always renders everything in a grid-like fashion, starting at the top-left corner and moving successively towards the bottom-right until it’s done placing all of your HTML content.
If you’ve ever had a slow internet connection, and watched as large stuff on the webpage would push everything rightward and downward, that is essentially “render flow” in action.
You can change this default behavior using CSS position.
CSS position is sometimes considered an advanced skill because it’s not as intuitive as
margin, etc., since it changes the natural “render flow” of the browser.
These are the possible values for CSS position:
Today we’re just going to look at
position: absolute and
position: relative since they’re perhaps the most versatile ones that will get you a lot of mileage once you feel confident with them.
When you make an HTML element
position: relative, it’ll remain “in the flow” of the layout but you can move it around!
position: relative you’ll usually want to define the
You can think of “relative” position as being: “relative to where it was initially positioned.” In this case, the green square is now
25px from the
25px from the
top of where it was initially going to be.
What’s also worth noting is that its width and height is preserved in the square grid. That means it’s still considered “in the flow” of the layout… it just got kinda nudged.
Absolute positioning is a very powerful CSS rule for moving HTML elements around. Sometimes yielding unexpected results:
The orange square is actually the 13th of these 25 squares (the one in the middle of the grid), but it looks like it’s the last square! Weird. Using position: absolute takes elements “out of flow” so its grid space gets collapsed.
Yea but why’s it all the way up there?!
The orange square gets placed at the 0x, 0y coordinates (eg.: the top-left corner). Just how browser rendering always begins at the top-left corner,
position: absolute elements use that as their rendering origin too. You can use
left properties to offset it from there.
But, you can also give it different originating coordinates…
In the example above, the parent element (
div.grid) has the
position: relative rule which causes the orange square to take that as its rendering origin.
While this may seem unintuitive behavior, it’s actually intentional! Allowing for this gives you a lot of control over where/how you arrange HTML elements…
Learn more about CSS Positioning on Mozilla Developer Docs
Hope you learned something here today. Please leave a comment if you have a question or have something to add and I will 100% respond to you.
Keep on coding 🙃
Howdy @sn236! Yes I suppose it is possible.
Relevent SO question = https://www.quakit.com/css-positioning-absolute
On this site I see that they use pixels with absolute. I know you can DEFINITELY use % and px. It just depends what your making and what you prefer. Either ways, thanks for the comment and upvote! :D