Single post in A Somewhat Extensive Guide to BBCodes

Heya! I wasnt really sure where to go for this, so I'm hoping this would be a good place. I'm in the middle of trying code a journal for myself. It seems that whenever you tab over, the tab box moves positions. Does anyone know what might be causing this? I'm still leaning how all this works and I've kinda been beating my head against this for a while with no good solution. I know the code might looked scuffed, so apologies if it looks scrunkly Here is the link to the code if looking at it will help figure out what is up. Thanks!