Hello Zan,
The problem that you are describing with the scrolling is likely the new "Natural Scrolling" feature in Mac OS X 10.7 Lion. To make a long story short, Apple has decided that it seems more natural (hence the name) to scroll the page UP by moving your finger UP - the same way you scroll on iOS devices.
If you would like to disable natural scrolling and return to the way people have been scrolling on computers for years, follow these steps...
If you use a mouse -
1 Open System Preferences on your iMac.
2. Select Mouse (second row).
3. Under the Point & Click tab, uncheck the "Scroll Direction: Natural" checkbox.
4. Your scrolling issue should be fixed.
If you use a trackpad -
1. Open System Preferences on your iMac.
2. Select Trackpad (second row).
3. Under the Scroll and Zoom tab, uncheck the "Scroll Direction: Natural" checkbox.
4. Your scrolling issue should be fixed.
As for the issue with the black text box on certain web pages, you might have a missing plugin. Usually, websites will have a link to download the plugin on their websites.
Hope this helps,
O.C.