Thanks for contributing to our forum. Perhaps other members of our Community will have some different ideas on how to accomplish this, but one thing you could potentially do to effectively set a fixed width for your description regardless of the viewer's screen size is add a table with a fixed width to the description editor and place your text within the table.
You can create a table using the description editor which is enabled in your account by clicking the “Insert/Edit Table” button on the description editor toolbar, which is the one located just to the right of the “Anchor” button.
Once you click the “Insert/Edit Table” button on the description editor toolbar, you should be presented with a window titled “Table Properties”. If you specify the number of Rows and Columns as “1”, your table will basically just be one rectangular box in which you can enter your description text.
I hope this helps. If you need any further assistance with your account, please feel free to contact our Customer Support team by mousing over the “Help” tab within your account and selecting the “File Support Case” option.