my preview button keeps dispearing....

[asharpsilence]

its there when i first start it up,
then it disapears along with the render button...
ive selected every tab (fractals, render...etc...) its simply not under the preview window where it should be...

im new to this and was following tutorials and they all say "hit preview button" but its not there...
have i clicked something by accident to make it go away?
help?

[asharpsilence]

i realize if i save the parameters and re open the program i can preview it in the very begining, ( it still goes away if i make any changes...)
but really is that what i have to do every time?