This may not be the answer you're looking for - but - people end up banned from sites because of their activity. Either they've done something against the site rules, or they've engaged in fraudulent activity.
As far as Yahoo goes - If you're sure you've done nothing wrong, it may be that someone else has been using your login details to 'damage' their site, and they've banned the user-name. Try registering a new login with them - if that works then you're good to go. If, it still won't let you in - they've barred your ISP. In which case - the only thing you can do is email their customer support centre, (there should be a link on their home page) and explain what's happened.
Ask them to investigate you recent site activity - they will have an 'audit trail' they can look through to see when you (supposedly) logged on - and you can match that with the times you know you were not on-line.
Good-luck with it anyway - let me know if you're successful.
They were barred from combat.
Barred Parakeet was created in 1853.
why was i barred from games in my favorites
Nothing Barred was created in 1961.
Barred Straw was created in 1775.
Barred pipefish was created in 1882.
Barred loach was created in 1846.
Barred moray was created in 1845.
Barred triplefin was created in 1982.
That depends on the situation. It can be temporary or permanent.
Barred Rock chickens are purebred. The word 'barred' is just a term for color. Barred means like white with gray stripes, for example. 'Rock' is the breed.
musical group = band barred = banned