user3507542 user3507542 - 1 year ago 262
HTML Question

Unable to get property 'style' of undefined or null reference

I have been looking online for a Watermark effect for my textboxes to get some help and found a piece of code which looks like the following :


function WaterMark(objtxt, event) {
var defaultText = "Username";
var defaultpwdText = "Password";
// Condition to check textbox length and event type
if ( == "tb_Username" || == "tb_Password") {
if (objtxt.value.length == 0 & event.type == "blur") {
//if condition true then setting text color and default text in textbox
if ( == "tb_Username") { = "Gray";
objtxt.value = defaultText;
if ( == "tb_Password") {
document.getElementById("<%= tb_TempPassword.ClientID %>").style.display = "block"; = "none";
// Condition to check textbox value and event type
if ((objtxt.value == defaultText || objtxt.value == defaultpwdText) & event.type == "focus") {
if ( == "tb_Username") { = "black";
objtxt.value = "";
if ( == "tb_TempPassword") { = "none";
document.getElementById("<%= tb_Password.ClientID %>").style.display = "";
document.getElementById("<%= tb_Password.ClientID %>").focus();


Then the HTML:

<asp:TextBox runat="server" ID="tb_Username" Text="Username" onblur="WaterMark(this, event);" onfocus="WaterMark(this, event);" />

<asp:TextBox runat="server" ID="tb_TempPassword" Text="Password" onfocus="WaterMark(this, event);" ForeColor="Gray" />

<asp:TextBox runat="server" ID="tb_Password" TextMode="Password" text="Password" Style="display:none" onblur="WaterMark(this, event);"/>

But for some reason when i run my code the Username box works fine but the password box comes up with an error saying:

0x800a138f - JavaScript runtime error: Unable to get property 'style' of undefined or null reference

I have been looking online for a fix and nothing is working?
Is this because my Textbox is linking to a CSS stylesheet?

Any help would be greatly appreciated.

Answer Source

Try this..

    document.getElementById(id).setAttribute("style", "color:Gray");
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