How does one join a number of recordings to make one long track?
Depending upon number and length, one option would be to File…Import each one as a separate track withing the one project. Then use the Timeshift tool (double-ended arrow) to drag each of them into their respective positions before finally, File…Exporting the assembly as a WAV and then as an MP3 or whatever output format you want. You could, of course, add a little fade-out/fade-in at the end of each piece to achieve a smoother transition from one item to the next.
Not to bother… 
Where are the “recordings” that you want to join?
What form are these “recordings” in?
It will eventually become important that you also say which version of Audacity you are using and what operating system you are using.
Im using the 1.3 version of Audcity and running XP with Chrome.When I use append to continue my recording,I find a flat line where the new recording should take off from?
Im using stereo mix so I can see the wave.
Will the recording atomatically continue from where I have left off,even though a flat line is showing.?
No. If you get a flat line then Audacity is not receiving audio data. You can easily check whether that is the case after the recording is finished by playing the flat line portion - I’d expect it to be silent.
You’ve still not said anything about your set up so I can’t make any suggestions as to why Audacity is loosing the connection or how to prevent it.
Im using the 1.3 version of Audcity and running XP with Chrome
I really do not what more to say about my set up? I thought that was everything I could say? 
Audacity 1.3.xx
The last numbers are important (look in “Help > About Audacity”)
What settings do you have in the Device Toolbar?
If you’re using the “Sound Mapper” option, what settings do you have in the Windows Mixer? (both the record and playback sections).
Do you know what sort of sound card you have?
Some sound cards (for example Realtek and SoundBlaster) have their own mixer control panel (look for an icon near the time/date on your Desltop). If your computer has such a thing, what settings does it have for the record and playback settings?
What exactly are you doing? Is there audio playing continuously while you stop the Audacity recording, or are you playing a video, then when it ends stopping Audacity, then starting a new video, then restarting the Audacity recording? What is the exact order of events? At what point does the Audacity recording meter stop indicating am input signal?
How are you activating “Append Record”? What buttons do you press?
Too much detail is better than not enough 
Audacity 1.3.xx
The last numbers are important (look in “Help > About Audacity”)
1.3.14_beta
What settings do you have in the Device Toolbar?
MME Realtek HD Audio output &realtek Audio input:Steroe Mix & 2 (Stereo)Input channels
If you’re using the “Sound Mapper” option, what settings do you have in the Windows Mixer? (both the record and playback sections).
Do you know what sort of sound card you have?
Would that be the Realtek
Some sound cards (for example Realtek and SoundBlaster) have their own mixer control panel (look for an icon near the time/date on your Desltop). If your computer has such a thing, what settings does it have for the record and playback settings?
What exactly are you doing? Is there audio playing continuously while you stop the Audacity recording-Yes,thats what Im doing, or are you playing a video, then when it ends stopping Audacity, then starting a new video, then restarting the Audacity recording? What is the exact order of events? At what point does the Audacity recording meter stop indicating am input signal?
When I begin recording again
How are you activating “Append Record”? What buttons do you press?
Well first I go to “my Music” and open the project,then I just press the “transport and then append” in order to continue recording
I did notice on the Realtek the"Sound playback" line volume was down to zero?
Thanks for the extra detail (though it still seems quite puzzling why the problem is happening).
I’ll move this topic to the Audacity 1.3 > Windows section of the forum.
Try this:
While music is playing, click on the recording meter, or right click on the recording meter and select “Start Monitoring”. (the recording meter is the one with a microphone icon in the bottom left corner). You should see the recording meter jump into life and shows a red bar moving up and down with the sound.
Does that happen?
Click the meter again to stop monitoring.
Then go to “my Music” and open the project
Then click on the recording meter, or right click on the recording meter and select “Start Monitoring”.
If the meter jumps into life and shows a red bar moving up and down with the sound then you should be good to record.
If the meter does nothing then Audacity is not receiving audio and it has nothing to record.
Steve,
I tried that and its working 
,btw the recording meter is more in the middle and towards the right hand side on this Beta.
Thanks for your time & patience