Hi,
First off, add this CSS:
div#left-sidebar{
height: auto;
}
To clarify: do you want the whole left sidebar sticky(including the search form)?
If so, try this CSS:
div#left-sidebar .inside-left-sidebar {
position: sticky;
top: 100px;
}
@media(max-width:768px){
div#left-sidebar .inside-left-sidebar {
position: sticky;
top: 50px;
}
}
If you only want the ads to be sticky, try this instead:
div#left-sidebar .inside-left-sidebar {
height:100%
}
div#left-sidebar .inside-left-sidebar aside#ai_widget-11 {
position: sticky;
top: 100px;
}
@media(max-width:768px){
div#left-sidebar .inside-left-sidebar aside#ai_widget-11 {
position: sticky;
top: 50px;
}
}