I found that at lines 72 and 80 the Response.Write statements contain an error where the "alt" HTML attribute is specified.
At both lines you can read something like:
.....alt=" & strTxtReadMessage & " border=.....
This doesn't raise an error, but in the case variable contains spaces (e.g.: "This is my alternative text"), the rendered HTML is incorrect, like
.....alt=This is my alternative text border=.....
and the relative tooltip shown by the browser, obviously, is This
The problem is the missing couple of double quotes.
The code should be similar to:
.....alt=""" & strTxtReadMessage & """ border=.....
which would be rendered in HTML as
.....alt="This is my alternative text" border=.....
and the relative tooltip shown by the browser, obviously, would be This is my alternative text