When loading the page, the block seems to jump out on the left, how to fix it?

Question

css

I'm making a shop . Already almost completed, but one garbage torments.
When the page loads, the block with the main content seems to jump out from left to right. It spoils the visual experience. Tell me, what is the problem and how can I fix it?

Answer 1

show content after download finished:

#hideAll
 {
   position: fixed;
   left: 0px; 
   right: 0px; 
   top: 0px; 
   bottom: 0px; 
   background-color: white;
   z-index: 99; 

 }

<div style="display: none" id="hideAll">здесь ваш контент</div>

 <script type="text/javascript">
   document.getElementById("hideAll").style.display = "block";
 </script>

Answer 2

Hang up a preloader.
PS Visual perception spoils the default scroll of the sidebar