How to call a webservice method from an html page [javascript] with out refresh the page

Use jQuery for performin POST or GET request from your html page like this :

function fun() 
{
   var data="hello";
   $.get("http://localhost/ws/service.asmx/HelloWord", function(response) {
        data = response;
   }).error(function(){
  alert("Sorry could not proceed");
});

   return data;
}

OR :

function fun() 
{
  var data="hello";
  $.post('http://localhost/ws/service.asmx/HelloWord',{},function(response) 
  {     data = response;
  }).error(function(){
  alert("Sorry could not proceed");
});

    return data;
}