Keyhan used to be a wellrespected newspaper in Iran. After the revolution it was seized by the government (though some of the editors coninue an exile version of the paper from London). Now it often posts questionable news.
Here is a picture of the Pro Ahmadinejad rally. Notice how it was photoshopped to make it seem more people actually showed up:
(you have to copy-paste the link, not sure why this workstation doesn't turn it into a link)
Here's some reasons why election might have been fraudulent: