A simple SEO guideline says that you should end your urls in .htm, .html or make them as mine. Some do not follow this and end them in .php, .asp and other programming languages. It might not be as good as the ones ended in .html, but Matt Cutts say they are and there’s no problem. Yet he stated clearly that URLs ended in .exe or .0 were not indexed at all until a few days ago. Now it seems Google does index them but we can’t be sure it [...]