I have a question... What happen If I copy someone else content but I change like 75% of the content to my own words? please excuse my english sometimes
Although an awful lot of content is little more than somebody elses words rewritten, it isn't a wise idea, especially if you inadvertantly start including statistics or quotes without the necessary referencing. I'm no legal eagle, but I would say that wasn't right. After all, that 25% is still somebody elses work is it not? Inspiration is (generally) fine, ripping off isn't is what it boils down to.
the publishers or writers could sue you which would cost a lot of money, not worth it for 25%. If you reference the contents i pretty sure you wont get in troublt
It's plagiarism first of all. Second, it's a derivative work, which is violation of the copyright's holder right to exclusivity. Is it so hard for you to do your own research and write your own work? It's not rocket science.
always try to write up your own content, never try to copy, it can get you in trouble if the other webmaster finds out which would also cost you alot!