You either have a concatenation bug or unexpected data in your database. You'll need to step through your code until you find the line that has the bug.
IMHO, you should consider using the StringBuilder rather than concatenations. 1) It's much easier to debug. 2) String concatenation is resource intensive as every concatenation creates a new copy of the string in memory.
For example, the following code first places the string <div class="tabbing-row1"> in memory.
ltNews.Text += "<div class=\"tabbing-row1\">"; ltNews.Text += "<div class=\"tabbing-row1-left\">";
The next line copies the above string to a new location in memory then adds <div class="tabbing-row1-left"> to the end. The memory now looks like...
<div class="tabbing-row1">
<div class="tabbing-row1"><div class="tabbing-row1-left">
The current code is small so it should not cause a problem but if you have a lot of string concatenation you can easily see how it eats up memory. The following lines of code make 3 copies of all the prior concatenations.
ltNews.Text += "</a>"; ltNews.Text += "</div>"; ltNews.Text += "</div>";
Nonetheless, the StringBuilder will clean up the code and reduce the chance of concatenation bugs.