A few tiny corrections:
1. Add in class ZCL_EXCEL_READER_2007 at method READ_FROM_APPLSERVER in signature raising clause.
2. Add in class ZCL_EXCEL_CONVERT at methods OPEN_FILE and WRITE_FILE exceptions at gui_download method and add in both methods signature raising clause.
3. Add in class ZCL_EXCEL_CONVERT a text 'A problem occurred when writen the file'.
4. Changed occured to occurred in the whole file.
5. Changed Schmöcker to Schmoeker in the whole file.
