On inspection, the above is not a good description of how to do this. A better description of how this would work is (in the description text)
Code:
<div id="Txt">Features:</div>
<img src="/images/yourimage1.gif" width="20" height="20"
onmouseover="CngTxt('Txt','image1 feature')"
onmouseout="CngTxt('Txt')"
>
<img src="/images/yourimage2.gif" width="20" height="20"
onmouseover="CngTxt('Txt','image2 feature')"
onmouseout="CngTxt('Txt')"
>
Then add to your stylesheet something like
#Txt {width: 100px; height: 50px; border: 1px solid black;}
as well as whatever other styling you want.
Save yourimage1.gif and yourimage2.gif in the base /images/ folder.
The js file in this case would have 'some standard text' be '' (two single quotes) because there is no text after Features: if not on mouseover.