Lets say you want to make 'Between' selected instead of 'Equals' when Advanced Search page is loaded the first time.
PHPRunner 5.0/5.1
Paste the following code to the end of the search page in Visual Editor (HTML mode, right before </body> tag). Replace text in bold with correct field name (case sensitive).
<script>
function setSelectedIndex(s, v)
{
for ( var i = 0; i < s.options.length; i++ )
{
if ( s.options[i].text == v )
{
s.options[i].selected = true;
return;
}
}
}
setSelectedIndex(document.editform.asearchopt_
fieldname,"Between"); ShowHideControls();
</script>