1. Open the file in Dreamweaver
2. Click CTRL + F, or go to EDIT > FIND AND REPLACE
3. Select “Current document” in “Find In” (You can also select the folder if you have multiple files.
4. Search in “Source Code”
5. Check the box labeled “Use regular expression”
6. Type “[\r\n]{2,}” (without quotes) in “Find”
7. Type “\n” (without quotes) in “Replace”
8. Press “Replace All”
BTW the cause for the blank lines is the way dreamweaver treats end of line breaks.
If you’re using a Unix server select LF (unix) for the line break.