See Attached example to recreate.

I edited main.cpp and add a.setStyleSheet("#web

"); in main.cpp
Create a QWebView* in mainwindow.cpp
Set the QWebView's object name to "web"
m_mainWebView = new QWebView(this);
m_mainWebView->setObjectName("web");

Expected to see:
I expected to see the 100% of the QPushButton under the QWebView.
This is only an example. I wanted to show that the QWebView was transparent in Qt 4.4.3 but the same code no longer is in Qt 4.5 rc1

Got instead:
The QWebView was obscuring the QPushButton.

More details:
I'm using a QWebView as a container. The container is a child control of the main window. This allows me to use HTML and JavaScript for my user interface.

I've attached sample code to run. Compile in Qt 4.4.3 and run. Then compile in Qt 4.5 and run. You'll see the difference.