Verified answer

Internet issues

Your computer time is wrong (most likely reason)

Wrong password

Somethings missing in %appdata% .minecraft folder

Check if internet is working good

Update your time if it is wrong

Make sure your using correct password

Delete the minecraft.jar folder, it won't delete your worlds but back them up because I don't want to be blamed xD

If it still doesn't work try be more specific

I had the equal drawback, however i realise easy methods to repair this your combat click your minecraft launcher and click on residences and likewise you click on houses and it's going to open this window you look by way of all the tabs untill you to find one announcing stuff about sixty 4-bit and ancient colours anything along those traces tick all of them and your reveal will enlarge for slightly, then it shall work if that doesn't work uninstall java and minecraft re-set up java then down load minecraft after java is centered and run minecraft launchers as a administrator

I had the same problem, but I know how to fix this your fight click your minecraft launcher and click Properties and you click on properties and it will open this window you look through all the tabs untill you find one saying stuff about 64-bit and old colors something along those Lines tick them all and your screen will enlarge for a bit, then it shall work if that doesn't work uninstall java and minecraft re-install java then download minecraft after java is installed and run minecraft launchers as a administrator