I had heard of it before, but now when my friend did it he dropped big time for few keywords and a little for few does that really happened, I thought it doesn't but few things are now stopping me from changing my design
Yes, a major change to any page previously indexed by Google might make it drop in the serps or fall out of them completely but this is usually temporary. I've noticed this before while performing SEO upgrades on various blogs but the serps have always bounced back and usually improve a little. In short don't worry about it in the long term unless your stuff disapears for 2 months or more, then I'd check to see if something has been overlooked on the SEO front of the new template.
It's probably a result of what changed with the new theme, not the simple fact that he changed it. For example: -- Same title structure -- Same H1 tags -- More external links (especially in the footer) -- More/fewer links in the sidebar All of those things (and more) can have an effect, and that's likely what did it.
I have recently changed my site's theme and yeah, my SERPs was negatively affected. Traffic dropped from 400 to 200. Not sure if this drop in SERPs was because of theme change or the little down time [3 hours] my site had.
Search engines traditionally respond negatively to website redesigns. You often temporarily lose your rankings, but they usually come back eventually. It depends on what things change when you install a new wordpress theme. A drastically different theme could change a lot of things. In the eyes of the search engine it seems like a whole new website is suddenly at that url. They need to verify that the website is still worthy of the rankings that they previously had. For example, if someone hacked a website and replaced it's content with pornography or other question content, the search engines don't want to keep directing people to that website.
changing in onpage seo will affect your SERPs. but it will be just temperaly. later your rank will be back to normal. this always happens to my sites as well.
No.You're only changing the layout, not the content...So, you can change your wp theme as many times as you can..(put the meta tags,etc same as in the previous theme).