Hi
These input fields (usename/password) are generated from the login.xml file located here: components/com_users/models/forms/login.xml
You can open this file and look for these fields:
<field name="username" type="text"
class="validate-username"
filter="username"
label="COM_USERS_LOGIN_USERNAME_LABEL"
size="25"
required="true"
validate="username"
/>
<field name="password" type="password"
class="validate-password"
required="true"
filter="raw"
label="JGLOBAL_PASSWORD"
size="25"
/>
change it to:
<field name="username" type="text"
class="validate-username"
filter="username"
label="COM_USERS_LOGIN_USERNAME_LABEL"
size="25"
required="true"
validate="username"
hint="COM_USERS_LOGIN_USERNAME_LABEL"
/>
<field name="password" type="password"
class="validate-password"
required="true"
filter="raw"
label="JGLOBAL_PASSWORD"
size="25"
hint="JGLOBAL_PASSWORD"
/>