Search engine optimization is basically a process of making a site optimized for top ranked search engine results so that it can be found among top results with using certain quality keywords.
Search engine SPAM can be understood as
• Any modifications that are done to a web page or site, solely because search engines exist, is spam.
• Whatever each search engine says is spam, is spam for that engine.
None of the so-called spam methods and techniques is in any way wrong or unethical. A technique or method only becomes wrong or unethical when it is used unethically or illegally; e.g. a page that appears to be about one thing but which automatically redirects people to something quite different i.e. called as Auto-redirecting.
Auto-Redirecting is the method or way of automatically sending surfers to a different page. Usually, the browser receives a page which contains the code to automatically load a different page.
This Auto-Redirecting causes to divert the user’s search result as a user want to search some related content, then this site is shown in search results but when user click on that link then he is directed to some other pages which is not asked by user, So that user is not able to get the right information. That is a kind of Search Engine Spamming.
There is nothing intrinsically wrong, immoral or unethical with any of the so-called search engine spam techniques and methods. In fact sometimes they help everyone. Until they are used unscrupulously, they help a page to be ranked more highly for its actual topic than it otherwise would. Surfers find the page in the top search results and go to the page's site. There they find what they want, having read the page's search engine listing. The surfer is happy, the search engine should be happy because it sent a surfer to a relevant site, and the page owner is happy because that site has a visitor. Like many other things in life, some of them can be used in unscrupulous ways but, in themselves, they are perfectly good, moral and ethical. Some of them are so good, moral and ethical that the search engines themselves use them when they auto-redirect visitors to a local version of the engine, and they do it by cloaking - providing different pages to different people according to some criteria; in this case it's the geographical location.
One more example of a search engine optimization method that some consider to be spam/wrong/unethical is hidden text. The reasons behind the hidden texts are to show some optimized text to the search engines but not to the people getting the pages in a browser. It is done because the text wouldn't make much sense to the people or it would spoil the design of the page. But there is nothing wrong with this technique. It doesn't attempt to hide anything from the search engines. The fact that they don't want it is irrelevant. The text is in plain sight to them and their programs. If they don't point it, that's their problem.
The fact is that so-called spam techniques are used to get the high page rank in the search results for its actual topic doesn't matter.
If the Search engines do it, then surely it is ok for the rest of us to do it. Yes it is! The method can be used unscrupulously where a person clicks on a link in the search results, they go to the actual page, but the page immediately redirects them to a page on an entirely different topic. The surfer ends up at a place where s/he had no intention of going. That's wrong, and it's a very good reason to be against misuses of the auto-redirect method, but it is no reason at all to be against redirects in general.
An example of a search engine optimization method that some consider to be spam/wrong/unethical is hidden text. The idea behind hidden text is to show some optimized text to the search engines but not to people viewing the page in a browser. It is done because the text wouldn't make much sense to the viewer or it would spoil the design of the page. But there is nothing wrong with this technique. It doesn't attempt to hide anything from the search engines. The fact that they don't want it is irrelevant. The text is in plain sight to them and their programs. If they don't spot it, that's their problem.
Search engine optimization techniques and methods are perfectly sensible, ethical and harmless, some engines don't want some of them to be used and, if they point them being used, they may penalize the page or even the whole site. Pages and sites are not often penalized. It depends on the nature of the 'offense'. Generally speaking, search engines are down an anything that adversely affects their surfers.