create a filter for a datagrid

[fcodebue]

I put into the toolbar a tab
first contains button for edit/delete operation
second contains: some checkboxes to applicate some detailed filter on load Data function...

Code:

<div id="toolbar" style="height:100px;"> 
  <div class="easyui-tabs" style="height:100px;"> 
    <div title="operazioni" style="padding:10px;"> 
      <a href="#" class="easyui-linkbutton" iconCls="icon-remove" plain="true" onclick="javascript:$('#elenco_clienti').edatagrid('destroyRow')">Elimina</a> 
      <a href="#" class="easyui-linkbutton" iconCls="icon-edit" plain="true" onclick="edit_it()">Modifica</a> 
      <a href="#" class="easyui-linkbutton" iconCls="icon-email" plain="true" onclick="email_it()">E-Mail</a> 
      <a href="#" class="easyui-linkbutton" iconCls="icon-print" plain="true" onclick="print_it()">Stampa</a> 
    </div> 
    <div title="filtro" style="padding:10px;"> 
      <form action="customer_list" method="POST">
    <input name="emissioni_atmosfera" type="checkbox" class="easyui-checkbox" style="width:50px">Emissioni atmosfera
    <input name="messa_terra" type="checkbox" class="easyui-checkbox" style="width:50px">Messa terra
    <input name="acque" type="checkbox" class="easyui-checkbox" style="width:50px">Gestione acque
    <input name="verbali" type="checkbox" class="easyui-checkbox" style="width:50px">Verbali<br />
    <input name="apparecchi_sollevamento" type="checkbox" class="easyui-checkbox" style="width:50px">App.sollevamento
    <input name="ipcc_aia" type="checkbox" class="easyui-checkbox" style="width:50px">IPCC/AIA
    <input name="cpi" type="checkbox" class="easyui-checkbox" style="width:50px">CPI
    <input name="formazione" type="checkbox" class="easyui-checkbox" style="width:50px">Formazione
        <input name="filtro" type="submit" value="applica" />
      </form>
    </div> 
  </div>   
</div> 

why submit button doesn't reload page posting checkboxes input variabled to filter datagrid loading data?