I try to edit it and it open to frontpage. after I edit it I click save and it say
Mircosoft Visual C + + Runtime Libary

Runtime Error!
Program: C:PROGRA~1/MRICO~2/Office/FONTPG.EXE

abnormal program termination




and when I click ok it pop up anotehr window say this

The instruction at "0x73dd11" refernced memory at 0x0000004". The memory could not be "read"

Click on OK to terminate the program


what do I do now? How can I edit it and save it?

Don't use frontpage...use a text editor. I can't remember, but I think you can set FP to recognize CSS files... not too sure though, but your best bet is to at least use a text editor for CSSing.