How to make a field required from the web to lead form.
If the validation is done within Salesforce, any forms submitted will be rejected by the database if they do not meet the validation rule criteria. This would prevent the record from being saved correctly.
Use the word 'Required' at the end of the syntax for the field. It should look like:
<label for="first_name">First Name</label><input id="first_name" maxlength="40" name="first_name" size="20" type="text" Required />
Example for a Picklist field:
<select id="00NA000000Abtqs" name="00NA000000Abtqs" title="Builder Name" required="required">
<option value="">--None--</option>
<option value="ABCD">ABCD</option>
<option value="WXYZ">WXYZ</option>
</select><br>
See Also:
Guidelines for Setting Up Web-to-Lead
Generate Leads from Your Website for Your Sales Team
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