I was wondering where the odd 88x31 size came from. According to this [1] it's basically because at one point GeoCities used a GIF of this size and then everyone copied it.
[1] https://ux.stackexchange.com/questions/140100/why-has-8831-b...
[1] https://ux.stackexchange.com/questions/140100/why-has-8831-b...