Telerik Reporting HtmlTextBox item does not support all HTML elements and CSS attributes. For more details about the item, please take a look at the HtmlTextBox
help article. Try using the dedicated for table structures items as the Table, List and Crosstab items
One way to have an HTML with the non supported elements would be to convert the HTML to an image and use that image in your reports with a PictureBox
item. Check out the HTML to Image in C#
If you need further help regarding Telerik Reporting, use our forum
or open a support ticket with your questions.
Have you tried the new visualization options in Telerik Reporting Q2 2013? You can get them from your account.