ASM80 is an Integrated Development Environment (IDE), aimed on assembler development for 8bit microprocessors, mainly 8080, 8085, Z80 and 6502.
ASM80 contains two main parts: Editor + assembler and Debugger. The whole IDE is web-based, which means you can work with it on every computer where modern browser is installed. You haven't download or install anything; all you need is a browser.
All your files are stored directly in browser, so you need no "account" to "access your files online". They resides in your browser and you can download them as a ZIP file and store to your local computer.
Assembler uses common core, which contains common preprocesor and parser, and specific translation modules for each processor. So the main directives (ORG, EQU, IF-ELSE-ENDIF, MACRO, REPT, DUP) are usable in all source codes for every processors.
You can use inline debuggers in assembler window, which provides basic debugging functionality (i.e. stepping or registry access). There are real computers emulators too, so you can test your programs directly in them.