Here's a link to an example of what I'm talking about:
Almost every time I make a new post in this category, I use the same table information. At first everything looks perfect, but if I go back to it a few days later, it comes out looking like this. The table columns span the width of my entire website, instead of staying in their own 700px wide table.
And see there's this example, which is the minority in this case, where everything still looks fine. The table columns are the right width and don't spill over.
It has the exact same table code. I have no idea what's happening, and can't figure out what's wrong. Any help would be appreciated. I'd like to keep it from happening in the future.