It is likely that you have left some tags without its
matching pair to start/end it. There was some text (maybe
blank) in between these, which is getting displayed.

mostly, it happens if you remove some part by global
replacement. Suppose you had some <Font ...>x</FONT> pair
and you removed <Font ...> part by global replacement, thus
x</font> got left there, and all these x are getting displayed.

It is more likely that such a part is left in some <table>
lines, so that it does not fit and html engine is pushing it up.

Do share the info about causes when you resolve it.