javascript html css django user-interface

CSS/JS Issue: Grey Space Appears Between Navbar and Content on Page Load, Then Disappears on Interaction

I'm working on a Django-based website and encountering an issue with a grey space appearing between my fixed navbar and the content on the home page. The grey space appears only on the initial page load, and once I interact with the page (like scrolling), the grey space disappears, and the layout corrects itself.

Here's what happens:

On initial load: A grey space appears between the navbar and the content.
After any small interaction: The grey space disappears, and the page layout behaves as expected.

What I've Tried: I’ve traced the issue to this JavaScript that adjusts the margin of the content based on the height of the navbar:

document.addEventListener("DOMContentLoaded", function () {
    var navbar = document.getElementById("navbar");
    var content = document.querySelector(".content");

    function adjustContentMargin() {
        var navbarHeight = navbar.offsetHeight;
        content.style.marginTop = navbarHeight + "px";
    }

    // Adjust margin on page load
    window.onload = function() {
        adjustContentMargin();
    };

    // Re-adjust on window resize
    window.addEventListener('resize', function () {
        adjustContentMargin();
    });
});

Problem:

When the JS is active, the page initially loads with the grey space between the navbar and the content. The margin-top gets applied, but it looks like it happens after the grey space appears.
If I remove the JS, the page loads without the grey space initially, but when I interact with it, the content shifts up behind the navbar.

What I Need:

I want the content to never overlap with the navbar, but also avoid the grey space on initial load. I need to:

Ensure the content stays correctly positioned under the navbar on initial load.
Dynamically adjust the content’s margin based on the navbar’s height if the window is resized.

Solution

It looks like your adjustContentMargin applies different margin-top to your content element.

possible quick fix: You've mentioned that this only happens on the pageLoad event, so try to remove the:

   // Adjust margin on page load
window.onload = function() {
    adjustContentMargin();
};

this should leave you with the happy flow you described, on page load no gray space, but after user interaction (scroll?) the adjustment will happen.

It seems that you want to achieve a navbar, that will be "fixed" to the top of the page once the user is scrolling, and when the user is at the top of the page the navbar should "be at the top" without causing layout shifts.

try to add a "ghost" element that will take the navbar space (mainly height i guess) this element can be a sibling of the navbar fixed element. (allowing it to take the needed space we currently using margin to compensate the gap with.

so html should look something like:

...
...
<div id="ghost-navbar" style="it should have the same dimensions as the navbar">...</div>
<div id="your-navbar" class="fixed-styled-element">...</div>
...
<div class="content"></div>
...
..

I believe this should help you achieve what you're after. and you won't need JS here to change your page layout causing unnecessary layout shifting because:

Navbar is always fixed now
Content element will always start after the "ghost" giving the feel the navbar will be fixed when the user scrolls, and when the user is at the top of the page they'll have the fixed navbar fits nicely into the "ghost" element position.

P.S make sure the ghost element has the lowest z-index if this is somehow changed in your code.

I hope this helps you. Cheers.