hi friends. suppose my domain name is http://www.xyz.com ok. when i have write xyz in google then google shows my website sitelinks. but when i have write xyz.com or www.xyz.com or http://www.xyz.com then my google website link not show me. so suggest me if i want to show my google sitelink in all ways. thanks in advance for your reply and your suggestion.
Google have never said what the criteria is to generate sitelinks. My guess would be simply that the version of your domain name that shows them has the most/best quality backlinks associated with it as anchor text.
You cannot control when sitelinks are displayed nor can you control which pages they pick to highlight as a sitelink. All you can do is BLOCK a URL from appearing as a sitelink in Google's Webmaster Tools. About the only thing you can do is have a good Information Architecture for your site with clear navigation to each of the major sections and hope the sections that you highlight in your own global navigation attract the most inbound links from other sites. My guess is that their algorithm for picking which pages to highlight as sitelinks is based on 1) which pages you link to the most on your own site and/or 2) which pages on your site other sites link to the most and/or 3) which pages on your site get the most click-throughs at Google. But there is no documented evidence to say for sure how they pick them or how they decide when to show them. You can read Google's official take on them here http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=47334.
That seems strange to me. Did you set preferred domain in google webmaster tool? If not, do it now. Hope it will help
You cannot pick which URL shows up in a sitelink via WMT or otherwise. You cannot change the link text for the sitelinks via WMT or otherwise. This is done totally at Google's discretion. All you can do in WMT is block a URL from showing up as a sitelink once Google has picked it as a sitelink (essentially, telling them to remove it). Once a URL starts showing up, if you block it then it typically takes several days for it to disappear and them to pick a new URL to replace it with. Been there... done that.