You could do that with a plugin i assume but why would you want that ? It's not a good method for blogs to have exact same titles, seo-wise at least.

Again, why do you need that ? Do you have like tens or hundreds of blogs ?

As like blogger.com i want a link to my main home page.
can you please tell me which plugin???
it is easy to using HTMl and PHP but I dont want to edit core files

Totally not tested, might or might not work but i guess you could do sth along the lines:

// get info from blog cache
$BlogCache = & get_BlogCache();
$BlogID= $BlogCache->get_by_ID( $id );
// #2 is the blog id for the blog having the default title
if ( $BlogID != 2 ) { 
	// we are not on the default blog so we want to change the title for the current blog
	$BlogDefault = & $BlogCache->get_by_ID( 2 );
	// get the title of the default blog#2
	$BlogDefaultTitle = $BlogDefault->get( 'longdesc', 'htmlattr' ); //blog_longdesc, blog_tagline, blog_name
	return $BlogDefaultTitle;
	// set the blog title to the title of the default blog#2 
	$Blog->longdesc = $BlogDefaultTitle;
}

pcind wrote:

As like blogger.com i want a link to my main home page.
can you please tell me which plugin???
it is easy to using HTMl and PHP but I dont want to edit core files

Btw, if all you want is a backlink to the main home page, you better use skin functions, instead of changing blog titles