Interested in Language
Is this sentence correct ?
On the bottom of the page or it should be at the bottom of the page ?
Welcome to the forum, PritiPawha.
Please note that On the bottom of the page would have been a better thread title.
The two alternatives you are asking about are not sentences, but phrases. The context of at least a full sentence would have been helpful.
I might say 'I spilt coffee on the bottom of the page', but I suspect you mean 'Page numbers appear at the bottom of the page'.
Don't leave a space before a punctuation mark.