This paper focuses on how to improve accessibility for Braille readers on Internet. We criticize actual technologies and show their limits in scientific Braille and Braille personnalization, especially in pedagogical situations. We present NAT Braille, a free software solution designed to respond to pedagogical specific needs. The transcribing process uses a set of customizable XSLT transformations and several XML formats. We detail the design of NAT Braille and the technologies used for transcriptions. Then we explain why NAT Braille improves personnalization in Braille rendering on Internet. We give the example of our Mozilla extension which is able to transcribe web pages including MathML markup, and is set up with adapted transcription rules taking into account the user's preferences. We conclude by raising issues related to our work.