Prueba con esto ...
resp seria : HttpServletResponse resp;
....
<a href="Login.do?action=
<%=resp.encodeUrl('LoginUser')%>" onMouseOver="MM_swapImage('Image111','','<%=reques t.getContextPath()%>/img/mni_home02.png',1)" onMouseOut="MM_swapImgRestore()"><img src="<%=request.getContextPath()%>/img/mni_home01.png" name="Image111" width="20" height="43" border="0" id="Image1"></a>