My email/webmail driving me out of my mind. I can only do one thing at a time

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and then it kicks me out. I have to enter my password again. Even on my alternate email/webmail site. I have to keep re-entering into the email/webmail by typing in my password. What do you think is going on and how can I fix it? It happens about 10 times. 9 it tells me nothing and the 10th time, it says, "503" error code. So how do I find this error code number and what it means? Also how do I get rid of the problem? It's driving me crazy. I look at an email, then I go to reply, I'm kicked out. Have to log into my mailbox again. Then I actually try to reply and I'm kicked out again. Have to log in again. It's also happening on my alternate email address. I didn't get high speed internet for this! HELP! Thanks for whatever you can do.