I have always had some general questions about how professionals export the final audio from sonar and also what format to export the MP3 for use on a web page.   
 
To create a wav to send to mastering service I selected all, exported to BUS, selected only the "master" bus.  Is that what we are supposed to do?
 
Also I exported to MP3  (I bought the MP3 add on or whatever from cakewalk).  I used 128 and slide the slider over the far left for highest quality.    That mp3 is on a web page.  I am noticing that there are some artifacts and some small areas that seem to speed up or little low quality areas and its seems to be random depending on which computer, browser or internet connection the computer is using.  Now I did not click that variable rate thing.  
 
How do "professionals" get ready to send to master wavs and ready to publish (premastered) MP3 for website out of sonar platinum?
 
The topic of getting audio setup for a web page can become very big, I just want to to know for sure I am doing things correctly.  As a third , side question.  How do professionals convert music for use on a web page or mobile device? the same MP3 lame encoder we all use?

By "exporting to a bus" do you possibly mean routing?
The most common way is simply routing all tracks and buses to Master Bus and use "Master" as the export source.
You'd better consult the mastering service about what they prefer, but it's common to export the project in 32 bits if it's going to a mastering service.
 
I know nothing about MP3s and those websites, but do note, that many web sites convert all the incoming MP3s to a lower quality, especially if you are using the free service. Paying something often gives you the option to upload higher quality. The safest way, I think, is to export a wav and then convert that to MP3 with whatever converter you're using. I'm not aware of any actual quality differences between converters, but as said, I know little about them.

Ok. That is what I do. The most common way is simply routing all tracks and buses to Master Bus and use "Master" as the export source.
 
I saw a few videos recently where they select the ENTIRE MIX  or the everything you hear preset to mix down for final wav to send out.  
 
I wanted to get the official final word from pros actually doing it.  OR CAKEWALK pros themselves.

When uploading to a site always upload the highest quality file you can. If you can upload a WAV great, but most will not let you. At least prepare a "384" MP3 and upload that. As already said, a lot of these sites are going to convert no matter what. Converting a 384 MP3 to a 128 MP3 will sound better than converting a 128 to a 128 for no good reason.
 
My preference is to only export the WAV file from my DAW. Usually a 44.1K / 24 bit but CD quality (44.1K / 16bit) is fine to. I create any other formats I need from that one as I never render a mix directly to MP3. I use SoundForge to create various formats, but there is nothing stopping you from importing the mix back into Sonar and creating an MP3 there.
 
Just my 2 cents...

I manage my own site(s) I can do whatever I want for the source file so I am using HTML5 audio wrapper with ogg, mp3 source formats, then a link to a high quaity wav for download.  The mastering place I use gives me a wav.  I just noticed some loss in the conversion.  Hey you said 384 MP3?  will everything play that? like phones, opera browser etc?  I guess I had not thought of upping the rate.

I export using all the default setting so I'm not sure what those are. I only change the bit rate down from 32 into 16. 
I master the song in Wave Lab 
I burn a CD with Nero
I use Gold Wave to convert to mp3. I use 160. I was told Sound CLoud uses 160 so if you use that then they don't re convert. 
 
Song might play back weird while streaming. Download the song and then listen to proof it.