Auto-complete fields in CakePHP show their results in div.auto_complete.

To return a result, send an un-ordered list.

Ajax component and Ajax::autoComplete are described in CakePHP Manual

 
div.auto_complete {
   position:absolute;
   width:250px;
   background-color:#fff;
   border:1px solid #888;
   margin:0px;
   padding:0px;
 }
 
div.auto_complete ul {
   list-style-type: none;
   margin:0px;
   padding:0px;
}
 
div.auto_complete ul li.selected { background-color: #ffb;}
 
div.auto_complete ul li {
   list-style-type: none;
   display:block;
   margin:0;
   padding:2px;
   height:16px;
   font-size:12px;
}
 

Link from here: http://wiki.script.aculo.us/scriptaculous/revision/Ajax.Autocompleter?rev=5