<script>
function doclick1(){
var txtN = document.getElementsByTagName("input");
for(i=0;i<txtN.length;i++){
if(txtN[i].type="text"){
txtN[i].readOnly=false;
}
}
}
</script>
<input type="text" id="contactus1" readonly>
<input type="text" id="contactus2" readonly>
<input type="text" id="contactus3" readonly>
<input type="button" name="button4" value="修改" onclick="doclick1();" />