大家看看display:column的问题怎么回事呀？急求

Question

<%
for(int i=0;i<t_roles.length;i++)
{

rolesname=t_roles[i].getRoleName();


%>
<display:column sortable="true" title="<%=rolesname %>">
                                                       <% if(rolesname==roles[i].getRoleName()){
                                                        %>
                                                        <img src="<%=imgPath%>ico/yz.gif" width="12" height="11" border="0"> 
                                                        
                                                       <%}else%>
                                                        <img src="<%=imgPath%>ico/yz.gif" width="12" height="11" border="0">
                                                       
                                                           
</display:column>
<%} %>怎么使得只显示图片 而不出现http:/*********/images/ico/yz.gif" width="12" height="11" border="0" /> 这样的现象 ？
谢谢大家帮下！！