AA, I see that your website is having errors which are unique only to your website, and not to the main forum software.
I just spent a few minutes looking at the source of your pages and found that you are not using table wrappers. Your table wrappers are completely blank. This element is key to displaying pages on UBB.threads.
On a fresh install of UBB.threads 7.6.0 to my sandbox server, I am able to duplicate your forum display issues exactly, by removing this key Wrapper element from the stock UBB.threads install.
Please Follow these instructions, to resolve your main forum display issue.
1) Go to your Control Panel
2) Go to Display Settings | Styles
3) Click on the "Wrappers" tab at the top
4) In the first row, for wrapper ID "0", NAME "default", click on the [Edit] link on the right.
5) Copy the following HTML blocks in to their correct sections:
Opening HTML
<table class="t_outer" style="width:100%">
<tr><td>
<table class="t_inner" style="width:100%">
Closing HTML
</table>
</td></tr>
</table>
6) Click on the "Update Wrapper" button at the bottom.
This should resolve your forum display issues. If not, please continue to step 7.
7) Click on the left tab, named "Styles"
8) Click on your forum's default style name.
9) On this page, click on the top item, "Name, Images & Wrapper" to expend it.
10) In this section, choose "default" from the Wrapper Set drop-down.
11) Click on the "Update or Add Style" button at the bottom.
done.
NOTES: While looking through your forum HTML with an HTML Validator, I noticed that the your custom header is opening, and attempting to wrap something, but it is not closing anything. I took a screenshot of your HTML for your reference.
This is not stock HTML, but was found on your pages. There is no closing HTML that I could find.
<table style="width: 95%;background-color: black;spacing: 0;padding: 1;align: center;"><tr><td>
<table style="width:100%;border-spacing:0px;padding:5px;align:center;spacing: 0;background-color: #c0b9a9;"><tr><td style="vertical-align: top;">
If I had to take a guess, whoever was managing your forums at one time, was under the impression that a "wrapper" was a "forum wrapper," rather than a "table wrapper."
Correct these issues within your custom HTML, and your pages should then display as intended.
Stock UBB.threads 7.6 validates without errors
