I have been doing SEO for a few pages and out of them there are 3 pages which is not stable changing the rank often. The ranking drops from google 1st page to 2nd page some times. All the pages are from same domain and I am doing same SEO activities for all these pages, out of these three pages there are high volume and low volume keywords both the keywords are not stable. Once it reaches the top of the first page the ranking drops to the second page or to the 10th position even after continuous work.
Can anyone tell me why this happens and provide me a permanent solution for this?