Set field to read only on EditForm

Solution: Open Sharepoint Designer, select “Lists and Libraries” then select the list, then select “EditForm.aspx” from “Forms” panel.

Select “Advanced Mode.”

Click “Preview in Browser” and set the value in the field to something distinctive (e.g. “Wokka Wokka”)

From the browser, select “View Source” and search for the distinctive text.

You will see something like this:

<input name="ctl00$TextField" type="text" value="wokka wokka" maxlength="255" id="ctl00_ctl00_ctl00_TextField" title="Title" class="ms-long ms-spellcheck-true" /><br />

Copy the value in “id” into the text below, then go back to Sharepoint Designer and append that text at the bottom of the EditForm.aspx file.

Click Preview In Browser again and the field should be read only.

<asp:Content ID="Script" ContentPlaceHolderID="PlaceHolderAdditionalPageHead" runat="server">
<script type="text/javascript">
function setControlReadOnly()
{
var elements=document.getElementById('ctl00_m_g_19d74208_fb82_4a74_a3b0_0c5d16ec6591_ctl00_ctl05_ctl00_ctl00_ctl00_ctl04_ctl00_ctl00_TextField');
if (elements == null)
{
alert("Could not set control to read only.");
}
elements.readOnly=true ;
}

_spBodyOnLoadFunctionNames.push("setControlReadOnly")
</script>
</asp:Content>