there is a cross mark adjacent to status of my sitemap in google webmaster tools. what is the meaning of this? no data for search query is available.
It means sitemap is not working and data of search query is not availabe means nobody is founding your site in search engine
If you use wordpress, just download sitemap plugin, and read "installation" there will be everything explained.
It means your sitemap is not properly installed. You need to create a new xml sitemap for your website. There are many free tools available on the internet to create xml sitemaps.
if it is a WordPress based website then there are a plenty plug-ins are available by which you can easily create a Google site map
it is because your sitemap is not available,,,, if your sitemap is present then while google crawls your site your site may be down...
Means Google crawler didn't find a sitemap at the location which you showed to Google. If you're sure there is indeed a sitemap at your mentioned location, then try re-submitting it; if you aren't sure then find out the exact location of sitemap, submit the new and delete the previous one.