Css Image Rollover Using "visibility: Hidden"

[juststones]

Hello,

I've read a lot about using CSS to hide text or images (Matt Cutts blog etc.) and I have a couple of questions about this issue...

I use this technique to hide an image which contains extra info about a product I sell.
When the user hovers over a text link the image with product info is shown.

<< Please see the "More Info" tab on http://www.galleryvandijk.com/tamara...tie_ta3_a.html to see this in action >>

MY QUESTIONS:
1) I use visibility:hidden to only show an image when the user hovers over the text link "More Info". Is this technique safe when considering SERPs and SEO?

2) Is use a span containing text (see html code below: Tamara Aladin - 'Tuulikki' vase) which is hidden until an user hovers over the text link "More Info". Is this technique safe when considering SERPs and SEO?

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The CSS-code I use (short version):
.gallerycontainer_b{
position: relative;

.thumbnail_b span
position: absolute;
visibility: hidden;

>>>> on rollover:
.thumbnail_b:hover span{
visibility: visible;

The HTML-code I use:
<div class="gallerycontainer_b"><div align="center"><a href="collectie_ta3_a.html" class="thumbnail_b">More Info<span class="popup_ontw">Tamara Aladin - 'Tuulikki' vase<br /><img src="../Images/glas_popup/ta_trood_info.jpg" alt="More Info" width="250" height="190"/><br />
</span></a></div></div>

Thanx!