the reason HTML seems to work even if it has syntax errors is due to browser having built in ways to parse the code meaning it will still show but most likely look way different then you would want.
the code may turn pink due to syntax errors
There are many answers to this question. The first step is normally a reboot, second, I would check witch task or service is taking up all the CPU cycles and check the system and error logs. The list goes on... I'm not sure how detailed you want to get.
FTP (File Transfer Protocol) can be used for a variety of tasks. For instance, webmasters using FTP for pushing updates/files to their websites can provide easy and straightforward changes to their services without the need to physically transfer files onto the host server. FTP should be used when you must update a file or files on a host server for a variety of reasons and you do not have access to the host server physically. However, FTP also has some inherent security risks which is why some webmasters/hosts chose to opt out of pushing updates through FTP in favour of physical file transfer.