Hello,
If you are planning to write a blog, then ignore this reply.
If the look and feel of the text doesnot matters to you (and uploading text is all that you wish), then
pastebins are a good choice (Google "pastebin" for more).
Also, IMHO it is not possible to upload text with specific font size as there is an option in all browsers to zoom in/zoom out text (e.g. [View] --> [Zoom] in firefox OR [View] --> [Text size] in IE etc.). If we interpret it this way, then font size of text in a webpage depends on text size settings of browser.
Hope this helps....
AmbrNewlearner