Try making changes that are inline with this explanation from here...
https://developer.mozilla.org/en/Can...al/Basic_usage

"...The <canvas> element has only two attributes - width and height. These are both optional and can also be set using DOM properties. When no width and height attributes are specified, the canvas will initially be 300 pixels wide and 150 pixels high. The element can be sized arbitrarily...

yes, you did not find a logic problem. if you have, you would try to address it yourself. I suggested other ways to structure your application so you can find the error in the code. the problem is actually that you are not seeing the error yourself. I get your point that you are asking for help, but you will probably benefit more in the long term from having a better ability to examine what you wrote than if I some random person on the internet...

Get rid of the bold tags in the middle of your javascript call, look before the function:
<a href="javascrip t<b></b>:createTag('b ','txtA')"><str ong>B</strong></a>

To simplify the inter-browser compatibility, use jquery and let the API do the work of figuring out those different commands for you.

I suggest you get the mouse position and calculations right. It probably does not have anything to do with canvas having an odd ratio. Are you really thinking that professionally developed software based on an industry standard is going to have this kind of problem built into it? Check your logic first.

I just spent a couple days getting the logic right in the code I was writing. I could not get it right on the computer before it...