Although I don't usually log out when I finish looking at MO on a random day, sometimes it happens that I need to log in again using my Open ID. I use a Gmail account for that, and sometimes (more often than I like) I make an error when typing the Gmail name and as a result I get labelled as new MO user "unknown". If I log out of MO and try to log in again, I don't get a prompt to start all over again with the log in (which is what I'd like) but instead if I try to use the Open ID then MO remembers I am "unknown" from a few minutes earlier. It is really annoying. The only solution I know to get a fresh Open ID prompt after messing up is to clear all my cookies. Would it be possible for the MO log in page to include a button that allows someone to log in as someone else, the same way that when you try to log in to Gmail there is a prompt to log in as another user (in case, say, you are using a computer of someone else who has a Gmail account)?

quid: I will try that and see how it works when I am at my office terminal (rather than at home), which is where the problem most recently occurred.

@Kcondrad:sir even thoughi am not an expert in mathematics,i am a expert in computer science,(as i hold a degree in it,and i won many medals,that i can claim clearly,as i know lots of programming and all the things related to it)
you have helped me a lot by giving answers ,and guided me nicely in my previous questions,
i try my level best to answer you,and its my great opportunity

in the case of your Gmail account you please do the following steps:
1)i think if the warning message is of that kind ,please log in to the gmail and click the Recent Activity ,which is present at the bottom right corner of the page,to be more precise,it shows a thing called "Last account activity: 10 hours ago" like that ,and click details which is present below it,it shows a big list of activity information sir,
please verify that is it you who logged in that particular time
and if you have activity ,i mean entry which you have not done,then its surely that someone logged in with your password,and your account is hacked,

if so immediately do this steps
1)change your password ,so that stupid hacker dont know your new password,so that he cant do anything more with your account
2Never use your Google Account password on another website. If you enter your password in an external website and it's compromised, someone could try to sign in to your Google Account with the same information.
3)use a secure connection when signing in. In your Gmail settings, select 'Always use HTTPS.' This setting protects your information from being stolen when you're signing in to Gmail on a public wireless network, like at a cafe or hotel
4)Never tell anyone your password; if you do tell someone, change it as soon as possible.
Use a strong password, and don't write it down or send it via email.
Run scans and change your password immediately after noticing any changes in your account that you didn't initiate.
Always sign out of your account when you're using public computers. Just click Sign out in the top right corner of the screen when you're done using your Google Account.
Clear forms, passwords, cache, and cookies in your browser on a regular basis, especially on a public computer.

and regarding keeping good password:
Your password is the first line of defense against cyber criminals. Follow these tips to create a smart password:

Use a unique password for all your important accounts
Use unique passwords for your accounts, especially important accounts like email and online banking. Re-using passwords is risky. If someone figures out your password for one service, that person could potentially gain access to your private email, address, and even your money.

Use a password with a mix of letters, numbers, and symbols
Using numbers, symbols and mixed-case letters in your password increases the difficulty of guessing or cracking your password. For example, there are more than 6 quadrillion possible variations for an eight-character password with numbers, symbols, and mixed-case letters -- 30,000 times more variations than an eight-character password with only lowercase letters.

Create a password that's hard for others to guess
Choose a combination of letters, numbers, or symbols to create a unique password that's unrelated to your personal information. Or, select a random word or phrase, and insert letters and numbers into the beginning, middle, and end to make it extra difficult to guess (such as "sPo0kyh@ll0w3En"). Using simple words or phrases like "password" or "letmein," keyboard patterns such as "qwerty" or "qazwsx," or sequential patterns such as "abcd1234" make your password easier to guess or crack.

Make sure your password recovery options are up-to-date and secure
Make sure to regularly update your recovery email address so that you can receive emails in case you need to reset your password. You can also add a phone number to receive password reset codes via text message. Additionally, many websites (including Gmail) will ask you to choose a question to verify your identity if you ever forget your password. If you're able to create your own question, try to come up with a question that has an answer only you would know. The answer shouldn't be something that someone can guess by scanning information you've posted online in social networking profiles, blogs, and other places. If you're asked to choose a question from a list of options, such as the city where you were born, be aware that these questions are likely to be less secure. Try to find a way to make your answer unique — you can do this by using some of the tips above — so that even if someone guesses the answer, they won't know how to enter it properly.

final important thing is that :"Check for viruses and malware. Run a scan on your computer with a trusted anti-virus software. If the scan detects any suspicious programs or applications, remove them immediately."


thanks a lot sir,
yours truly,
iyengar

but please check whether your gmail account is good or in hacked state sir,please do it immediately if you think your account contains some valuable information