w3.org reports errors for

Hello!

My website is akdh-ev.de

I tried to correct and update my website to get a better ranking for my website. I am using the newest joomla and jfbconnect. At the moment I an trying to correct all html errors and warnings. The w3.org validator found some errors:

1. Error: Attribute alt not allowed on element input at this point.

From line 846, column 29; to line 847, column 62
<input name="username" tabindex="0" id="sclogin-username" class="input-block-level" alt="username" type="text"↩ placeholder="Benutzername">↩

2. Error: Attribute alt not allowed on element input at this point.
From line 854, column 29; to line 855, column 58
<input name="password" tabindex="0" id="sclogin-passwd" class="input-block-level" alt="password" type="password"↩ placeholder="Passwort">↩

3. Error: Attribute alt not allowed on element input at this point.
From line 865, column 33; to line 865, column 131
<input id="sclogin-remember" type="checkbox" name="remember" class="inputbox" alt="Remember Me" />↩

I am not sure how to handle this. Can this be corrected or is it ae error in the template?

Kind regards,
Volker