Yey! At least now we know where to look Try this:

Block cookies
To set whether Safari blocks cookies in iOS 8, tap Settings > Safari > Block Cookies and choose Always Allow, Allow from websites I visit, Allow from Current Websites Only, or Always Block. In iOS 7 or earlier, choose Never, From third parties and advertisers, or Always.

You could try:
For iOS8 - select either Always Allow or Allow from websites I visit
For iOS7 - select Never

My source: http://support.apple.com/en-us/HT201265

 

Have IOS 8 ...tried it, but doesn't work!😱

 

Ah You may private browsing enabled which would not save the user name and pwd. So try this:

Go to Settings > Safari > Passwords & AutoFill, then turn on Names and Passwords.
Return to your Home screen and open Safari. If Safari is black or dark instead of white or gray, Private Browsing is turned on.

To turn off Private Browsing:
Tap the the plus + symbol in the upper-right corner of the Safari page, then tap Private in the lower-left corner.

Safari isn't automatically filling in account names and passwords on some web sites. To enable AutoFill:
Go to Settings> Safari > Passwords & AutoFill and make sure that these two settings are turned on: Names and Passwords > Always Allow
Return to your Home screen and open Safari. If Safari is black or dark instead of white or gray, Private Browsing is turned on (see above)

Source: https://discussions.apple.com/thread/6088083