Thank you for your post.
I am running FileMaker Pro 10 on an iMac with Mac OS X 10.5.7. I have done the following:
1. On one of my layouts, I created a Tab panel with three tabs: "FileMaker", "Google", and "Ebay".
2. In the first tab panel, I added a Web viewer with the address "http://www.filemaker.com"
3. In the second tab panel, I added a Web viewer with the address "http://www.google.com"
4. In the third tab panel, I added a Web viewer with the address "http://www.ebay.com"
When I go to Browse, the first tab panel is active and the FileMaker, Inc. web site loads and displays. When I click on the second tab panel, the Google web site loads and displays. When I select the third tab panel, the Ebay web site loads and displays.
Can you provide more specific information, and I'll try to duplicate the problem here.
Perhaps the web viewers only "look" like they're part of a tab control.
Try this test in layout mode: use your mouse to drag just the tab control. If the web viewers are properly placed so that they are part of a specific "tab", they will move when the tab control is moved. If they stay in place when you move the tab control, they aren't really part of the tab control, perhaps a pixel or two of the viewer is not inside the limits of the tab.
Many thanks PhilModJunk and TSGAL,
It was indeed a layout problem though not as you suggest to do with the placement of the web viewers but of the tabs themselves which I unwittingly positioned as slightly overlapping into the header field. Moving them safely within the body layout seems to have resolved all the flakey behaviour. I'm much obliged for your putting me on the right track.