Differences between Browserlab ie7 & ie developer tools browsermode: ie7 + onion skin problem

Question

Hi, 
I've just noticed display differences between what I see in browserlab for ie7 and what I see using ie9, but in browsermode:ie7.  I would have thought they would show the same as both are supposed to represent what the webpage would look like in ie 7.  Please can someone explain:
a) why they should be different,
b) which is the correct one.
Basically the Menu is perfect in BLab, but is floated left in browsermode:ie7.
There is nothing out of the ordinary in the code for this page, just html, css, a tiny bit of javascript & some php.
I am using windows 7 on a PC and the problem occurs if I use BLab through Firebug or directly from Dreamweaver.
The url is my old site that I am in the middle of updating, but I still get the same error with the new site that I am testing locally:
http://www.laughingrabbit.co.uk/
Kind regards
I am also having a problem with the onion skin feature, which I had about 2 months ago, but which then went when I deleted the cache and rebooted - no such luck this time.
When I try and show 2 browser views over each other, only one will show when I slide the slider bar making direct comparison impossible - both views stay the same as the one on the left. 
eg try http://www.laughingrabbit.co.uk/contact.html  The corners of the form should be rounded only in later versions of ie, as it isn't supported in earlier version.
It is the same either through the main BL interface or Dreamweaver.
I have tried closing down BL, deleting cache etc (the usual stuff), but it doesn't make any difference.  I work on a PC.
Has anyone else had issue with this and if so, how did you solve it.
AND YES, I AM SLIDING THE SLIDER FROM LEFT TO RIGHT and all over, but ti makes no difference
regards
Bek

Answer 1

hi Mark,  Here is one example, on my new site.  I have used css3 to round the tabs in the navigation which works for FF5, but obviously not for ie7, but no matter how much I slide the slider accross the image (and the tabs) never change.  i get the same whenever I try and use onionskin at the moment - the image doesn't change from the one on the left hand side.  If I swapped FF5 & ie7 round (as per the image) then the rounded tabs change to square as you would expect in ie7, but don't change to rounded as you slide the slider to the FF5 side.
kind regards
bek