\0020 will only work if the space glyph is correctly encoded. If you have a glyph in the font called ‘space’, try running the Assign Unicode command from the Glyph menu. This will assign Unicode values to glyphs based on their names, following a mapping list (the default will be the STANDARD.NAM file that comes with FontLab).

Also note that in preview and metrics strings etc. you can also enter a glyph by name, using this convention: /space

Thank you for the advice , that works.

Another question: how, could I remove the red measurement line in Fontlab. This line seems to me little useful. Is there anybody who can help me to use it effectively?

Thanks

This is quite funny, because I am pretty doing the same thing. last night after I finally got all my main glyphs into fontlab I ran into the exact same problems (and have also been refering to Learn Fontlab Fast).

Your not alone!