Next to %26quot;User names and passwords%26quot; click the Edit button.
Scroll through the list of sites until you find the site in question. It should say %26quot;Passwords Never Saved%26quot; in the User Name column. Click on that entry to highlight it and click the Remove button. Click %26quot;Done.%26quot;
That should do it. When you revisit that web site and enter your user name and password, Safari should ask if you want to save them, and of course this time you'll want to click to say yes.