Display problem

You have something strange:

<a href="[url]" title="[title]" class="upprev_thumbnail" rel="Summer 2013 anime PVs (Promotional Videos)"></a>
<a href="[url]" title="[title]" alt="Chuunibyou demo Koi ga Shitai! Movie Coming September 14th"><img width="48" height="48" src="https://haruhichan.com/wpblog/wp-content/uploads/chuu-2001-64x64.jpg" class="iworks_upprev_thumb wp-post-image" alt="chuu 200" title="Chuunibyou demo Koi ga Shitai! Movie Coming September 14th"></a><h5><a href="https://haruhichan.com/wpblog/index.php/4124/chuunibyou-demo-koi-ga-shitai-movie-coming-september-14th.html" rel="Summer 2013 anime PVs (Promotional Videos)">Chuunibyou demo Koi ga Shitai! Movie Coming September 14th</a>

Empty a tag with expected class, and secound one, without any class.

For better view I changed links and titles to shorties.

Maybe check other plugins? Is anything what change thumbnails? or thumbnail links?

Nope, no plugins to change thumbnails/links. Maybe it’s the theme? it comes with it by default.

Maybe it’s the theme?

Mayby. Could You try default theme for a moment? And check page source for double `a.

Uhm, I cant since it’ll cause many problems with plugins sadly…

https://www.haruhichan.net/?p=138 just changed to default Twenty Twelve theme on this site and it works perfectly. but when I switch to mantra the errors occur.

just changed to default Twenty Twelve theme on this site and it works perfectly

If works perfectly to 20/12, that is the problem:

but when I switch to mantra the errors occur.

And I can’t help ??

It’s fine, I fixed it with this:

/* Mantra Custom CSS */
.upprev_excerpt.upprev_thumbnail > a {
float: left;
margin-right: 10px;
}