3) Keyword Repetition : Repeating your keywords in the meta tags might boost your search engine ranking.
For Eg. “mobiles, models, accessories, USA, mobiles” might perform actually well than “mobiles, models, accessories, USA”.
But also care must be taken to see that you don’t repeat the keywords that often, else the search engines will blacklist you. You can repeat the keywords, but take care that no keyword is repeated more than two times and also you repeat only those keywords which are most important and related to the site. You can use compound keywords like “mobile, accessories, mobile models, USA”, as the search engines considers both the entities “mobile” and “mobile models” as different. But be moderate in its use, as some of the search engines don’t use compound keywords and you can get blacklisted due to it.
4) Keyword Drowning : This activity does not play that important role in getting the site blacklisted, but of overlooked it can have adverse effect on the SEO of the site and some search engines might even ban the site due to this reason.
If there are too many keywords in the meta tag then we can say there is higher probability of the occurrence of keyword drowning. To have 10-15 keywords in the meta tag is good. If you increase the figure upto 20, though its not recommended but still can work well. But if you start including 30-40 keywords in the meta tag then you get into the trap of keyword drowning. Stick to include only 10-15 keywords in the meta tag as it can generate fruitful results, don’t get yourself and the site trapped into the jungle of keywords, as the essence and the effectiveness of each keyword is diluted.
Thus the basic intent of search engine optimization is getting your website listed in the search engine. But the above highlighted points are the basic mistake that the web-masters make in the greed of getting higher search engine ranking. Thus one need to take proper care in playing with the keywords.