Board Thread:Support Requests - Getting Technical/@comment-26840207-20151108191646/@comment-154566-20151109003337

You could set the table's style attribute to "width:100%".

A word of warning, "100% at all times" can have unintended consequences in Monobook in wide screens. You might get better results by reserving a width on cells with collapsed images, which will be sufficient to keep the table from resizing.