I've not logged my exact actions. I've used the standard Linux installer.
I'm pretty sure that this problem did not came out immediately on the first start of the LAMP server, but on one of the following times. It is installed on my laptop and it is not continuously running.
I suppose that some files, probably something involving CSS, could have been corrupted, not during the installation but later.
If you know what are the files that control that page' styling, maybe I can try to check if they are all right.