I want to make a custom error page. For some reason my computer won't let me save a text file as just .htaccess it keeps saying something about a wrong file extention. What am I doing wrong???

use normal notepad to create file.
File
Save As
choose "all files" as the type.
enter ".htaccess" as the filename (with the quotes around it too)

And if that fails, upload it, then re-name it through your FTP