no follow tag for paragraph? i have one website. i have 10 paragraph on that page. but i wish search engine cannot read that 2 paragraph and use can read this 2 paragraph? is that possible with particular paragraph? i need to add something in robots.txt? or any other way?
If I understand you correctly, you want to substitute (replace, change) text based on whether the visitor is a person or a search engine crawler. To do this, you would use a scripting language (javascript, vbscript, php, asp.net, etc). I don't know of any tool for people who do not know at least HTML coding. The code must check visitor credentials and then serve content based on visitor type (checks 'is_crawler = true or false'). If the visitor is a crawler, then display 'this' text. If not, display 'that' text instead. If this is done to load your content with keywords for search engines, or to otherwise trick search engines, then it is called 'cloaking' and it is something that your site can be banned for. It is a common Black Hat technique.
Use Javascript to load the text when your user arrives. You can do this using an onLoad event in the body tag and by referencing an ID of an html element in your script.
It can't make possible by the use of the robot.txt setting, coz it is designed to order of the whole page and not for the portion of a paragraph. So as member longcall explained, you should use a script designed and coded in jave, php, asp etc. to stop the crawler of search engines and not the user. By the use of that it may be possible to stop the crawlers to go there.
Use Javascript, if you can't figure out how to do it you can probably hire someone to do it for super cheap.
yes, only use is use on-page stuff like javascript, flash etc. If you use program detect user-agent, will more like a doorway page