Tammy, can you give me more details like screenshots for better understanding?
If you may provide us with the list of exact steps we should follow to reproduce the issue, this will really help us to fix it.

this problem was reported and to be fixed long time ago 
sometime when you open a new chat message the ,new message shows below the line and you can not read it 
on click im the send box as soon as you type the first letter the message jumps up and you can then see the message 
the same happens in mail box 

in chat



in mailbox

my messages not hidden, using sigma theme , but I don't like this message jumping.

Tammy, try to disabling Smileys plugin and check whether the issue still persist. And please provide me with the link to the topic where this issue was mentioned earlier.  

il try smilies 
i posted this problem long long time ago when 1,6 come out 
i could find it but would take me a wile 

Tammy, please check whether you may reproduce this issue on our Demo.
If yes, then please provide us with screenshots from Demo site and  info about the browser name and version you're using.

DeFender, please check whether this issue persist when you use default theme, for example the Origin theme.