xls file format is not valid

Keyword Analysis

Keyword	CPC	PCC	Volume	Score	Length of keyword
xls file format is not valid	0.41	0.6	6338	51	28
xls	0.08	0.4	6874	99	3
file	1.27	0.9	7796	55	4
format	0.25	0.3	1549	34	6
is	0.58	0.5	7827	78	2
not	1.16	0.4	2247	24	3
valid	0.41	0.9	7060	72	5

Keyword	CPC	PCC	Volume	Score
xls file format is not valid	0.3	0.9	1232	45
xls file format is not valid error	0.83	0.7	4837	50
file format is not valid excel xls	0.17	0.1	6660	47
excel file format is not valid	0.24	0.8	1054	67
microsoft excel file format is not valid	1.6	0.6	3381	44
cannot open xlsx file format not valid	1.09	0.9	8150	7
file format extension is not valid excel	1.34	0.3	499	87
excel error file format is not valid	2	1	2847	90
excel file format or extension not valid	0.98	0.5	3800	88
excel format is not valid	0.86	0.3	7416	88
xlsx file extension not valid	0.84	0.7	636	55
excel file extension xlsx not valid	1.06	0.3	8167	32
excel format extension not valid	0.76	0.4	4037	87
xls invalid file format	1.57	0.3	9218	71