To import products successfully, it all depends on how the template and the file to be imported is setup. There are a few requirements that apply:
Use only CSVI supported fieldnames
Use correct delimiters when importing CSV files or make sure there is no empty column data when importing XLS files
Only import file sizes your system can handle
Format your data correctly
CSV Improved can only import fields that are listed in the available fields list. It is not possible to use your own fields. The only exception here is custom database fields in the product table. This is a new feature as of the 0.9 version.
For CSV files it is important to have the correct delimiters. The template and the file to import must have the same delimiters. For example, the template has the delimiters ” and , while the file to import has ^ and ~, the import will fail.
For XLS files, spreadsheet programs do not always clear empty fields. For example, the columns A till D are filled and in column E there is some test data. Before importing the data in column E is deleted. This looks deleted but the fields are actually filled with an empty value. This will cause the import to fail because it reads the empty values. Make sure all data is really deleted, by deleting the complete column instead of just the fields.
Size does matter
The size of the file to import is very important. How big the file should be to upload depends on the server settings. Most important is the amount of memory available and the maximum execution time. The larger the file to import, the more memory and time is needed to process it.
CSV files use a lot less memory than XLS files. This is because the CSV file can be read one line at a time, the XLS file needs to be read in full on import. As the import process collects data on the import, memory is used more. This is usually about the size of your import file. Unfortunately, there is no exact science as to calculate the amount of memory used.
Format your data
All data should be formatted correctly. The available fields page gives information per field on how the data should look like. If data is not formatted correctly, the import will still happen only the data will not show up as expected.
An example of how a CSV file could look like: "product_sku","product_name","category_path","product_desc","product_price","product_full_image","product_thumb_image"
"PIE1","Apple pie","Pies/Apple","A delicious apple pie","9.99","appliepie.jpg","resized/applepie.jpg"