Title on Tag Page on articles2u blog

[articles2u]

Title on tag page display name of the blog. It not display Tag Title or Title of the tag page.

My Title code on Header is

<title>
<?php if (is_home())
{
bloginfo('name');
echo ' -- ';
bloginfo('description');
}
elseif (is_single() ) { single_post_title();}
elseif (is_page() ) { single_post_title();}
else
{ ?>
<?php wp_title(' '); ?>
<?php if(wp_title(' ', false))
{
echo ' | ';
} ?>
<?php bloginfo('name');
} ?>

</title>

If i use
elseif (STP_CurrentTagSet()) { single_post_title();}
It display Tag title and blog name without space.
ex: TagBlogname (no space).

Please help me.