Tutorial Part 2b - Framesets and Frames

An HTML document can contain either the FRAMESET element or the BODY element, but not both.
(I know I said in Part 1 that all HTML pages should contain a <BODY> tag, but I was lying - it was for your own good <g>)

FRAMESETS contain FRAMES - which are like pages within a page. The SRC attribute of a Frame points to a web page that is loaded into the frame.
Not all Browsers can handle FRAMES, so FRAMESET may also contain an optional <NOFRAMES> tag which may contain HTML that is [only] shown by such browsers.
The FrameSet divides the available page 'real-estate' between the different Frames vertically (cols attribute) or horizontally (rows attribute). You can specify col and row sizes as absolute (pixels; points; cm's; inches; &c.) or relative (%age) units.
FrameSets can be nested (but don't overdo it).

Take a look at how this page is made up:

If you have clicked anywhere on this page you may be in one of the Frames - so Click on the Refresh button in the ToolBar or select 'Refresh' from the 'View' menu
Now Select 'Source' from the 'View' menu - and you will see the FRAMES and FRAMESET defined in the main or Outer page.
The Frameset divides the page vertically into two Frames ('margin' and 'mainPage') and these link to 'marginT.htm' and '_tutorial.htm'. There is a NOFRAMES tag which shows the customary 'sorry' message.
Close the Source page when you have finished and Click somewhere in either of the Frames
- Now rightClick on the page and select 'View Source' from the drop-down menu
Close the Source page

Question: the main page specifies '_tutorial.htm' as the source (SRC) for mainPage, but it now contains '_T2b.htm' - how did that happen (Hint: look at the HTML in marginT.htm)