I was wondering how I can call multiple external css files at once instead of calling each individually. I want to do that to avoid the request number and minimize it to one
You can use the @import
statement inside your 'master' css, to make it include multiple files at once. All you would have to do is link to your one master file in your HTML.
However, this will not limit your requests. As long as they are separate files, you will have to do separate requests.
For real performance improvement you would have to merge the files into one bigger file. There are some good tools out there. I prefer LESS, which is a precompiler that does lots more, but can also merge multiple files into one (minified) master css