On one side of Internet Marketing; Spammers keep on implementing Black hat SEO tricks to play with major search engines while on other hand Google guys keep on refining their Algorithm to give complete Fight back to beat these Spammers.
So this is all about Search Engines and Spammers & in between comes real SEO guys those work hard according to Google guidelines and optimize websites for stable longer length. Any ways come to point I was talking about Meta Tags.
Nowadays most of the Major Search Engines do not give any special attention or preference to them. They no-longer have significant effect on website's SERPs or Rankings, there are hundreds of other activities that plays vital role while doing On page Optimization like: Titles, Proper use of H tags, Website Navigation Architecture, Bold,Italic Fonts, Font Size and so on..
Meta Keyword: This tag is meant for putting your unique keywords related to content of your web page. Or they just give fair idea about the whole content of your web page, and search engines can have idea: "what this particular page is all about".
BUT what most of people start doing, they started using this tag tag as a source of their web page promotion in unethical way .
Most of spammers use to stuff this Tag with most competitive keywords for their web-site without regard to available content on web page Without regard to length of this Tag.
Some keep on stuffing same keywords with multiple repetitions to Meta Keyword Tag so that they will cheat search engine spiders and will rank well for those keywords.
By the time Google detected all these kind unethical promotional activities so nowadays they started neglecting Meta Keyword Tag. So this Tag can be neglected.
Meta Description: This Tag gives abstract of Web page so that visitors cn have fair view : what this page is all about. This tag still has some importance as most of search engines use content available in this tag as Snippet and same is mostly displayed on SERPs.
BUT again most of people stuff this tag with their competitive keywords that doesn't even make any sense, without considering or bothering about recommended length of this Tag and tries to cheat search engines.
If you have unique and quality content on your site then you can even ignore this tag because search engines will pick automatically most relevant content from your web page that matches the Query entered by users. So this tag can also be neglected.
Meta Title: This tag acts as Identity for web-page, gives clue about the whole discussion of page or purpose of web page. Google displays Title Attribute of page as title in SERPs, please remember here I'm talking about Title Attribute of Web Page and not Meta Title Tag.
If you have prepared well defined and appropriate Page Title attribute then there is no need to put this Meta title tag on you web site.
Mostly people keep Meta title Tag and Title attribute of web page exactly same, and they should be. Search Engine gives preference to Title Attribute but not to Meta Title Tag of web page..so again this tag can also be neglected.
So if you are going to start On page Optimization for any site i would recommend do not waste your time on preparing these Meta Tags instead work hard on refining your Industry keywords, Build Powerful, unique Quality Content and utilize your time on improving rest of On page factors for your web site that will give you worth results than these Meta Tags.
SEO & Internet Marketing Specialist