CSS Bagaimana membuat sesuatu tetap di layar

#id /*or*/ .class /*or, not reccomended*/ element{
  float: left;   /*or*/
  float: right;  /*or*/
  float: top;    /*or*/
  float: bottom; 
  
  width: 20%;
  /*best to use this for something like a div/container, 
  so everything inside it will float like a navbar or
  sidebar. */
}
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