Thanks Steven and Mike for your the quick responses.
I could partly solve the problem - (for the portfolio + gallery page):
1. It seems that you're right concerning the missing flash plugin for FF 3.6.12, I have to verify that, I thought it will use the same as every other browser on my machine. So I will try once I managed to install the FF-Flash version.
2. Concerning the wordpress problem, it still exists for www.sms-photo.de/wedding/welcome/ .
BUT it is gone for www.sms-photo.de/wedding/galerie, after inserting the <script> stuff into my wordpress themes header and using <div style="width:100%"> [simpleviewer ...]</div> the page works fine now.
I was not aware that the simpleviewer wordpress plugin uses another method to display the gallery then the standalone version. And I still wonder why other browsers can live without the <script> definition in the header, even other versions of firefox seem to live with it without any problem.
However http://www.sms-photo.de/wedding/welcome/seems to still have a problem to display the simpleviewer gallery. Although I copied and pasted the exact same code I used for the now working galerie-page. Here are the pro options, maybe FF has a problem with anyone of those:
flickrSetId="72157625275660198"
flickrImageCount="150"
titlePosition="NONE"
captionPosition="NONE"
buttonBarPosition="OVERLAY"
buttonBarVAlign="BOTTOM"
buttonBarHAlign="CENTER"
showNavButtons="false"
showAutoPlayButton="false"
buttonBarScale="1.4"
buttonBarBackOpacity="0.5"
buttonBarPadding="20"
showImageNav="NEVER"
showToolTips="false"
imageScaleMode="NONE"
showOverlay="NEVER"
imageTransitionType="CROSS_FADE"
imageFrameStyle="SQUARE"
autoPlayOnLoad="true"
imagePreloading="ALL"
imageClickMode="NONE"
thumbNavPosition="CENTER"
captionDropShadow="true"
flickrTitleFontColor="#FFFF00"
flickrTitleFontSize="30"
captionPadding="20"
imageNumberFontSize="10"
thumbFrameWidth="0"
thumbLoadBarHeight="10"
imageNavStyle="CURSOR"
captionFontSize="15"
thumbHoverFrameWidth="2"
hideOverlayOnTransition="false"
lockBottomStack="false"
flickrImageSize="MEDIUM"
flickrUserId="31979337@N02"
enableKeyboardControls="false"
lockTopStack="false"
stageHPadding="0"
stageVPadding="0"
stageVAlign="CENTER"
displayTime="3"
autoPlayThumbs="false"
showAutoPlayStatus="false"
stageBorder="0"
enableLooping="true"
randomizeImages="true"
dropShadowStrength="0"
imageCornerRadius="50"
backgroundScale="NONE"
flickrShowTitle="false"
flickrShowDescription="false"
imageDropShadow="true"
imageTransitionTime="1"
backgroundColor="7C0B0B"
I am talking about Firefox 3.5.14. (Flash is installed as the portfolio page works just fine)