HTMLCleanUp is the webmasters's best friend!
It helps you solving a number of the typical problems you meet every day (or at least frequently) as a webmaster - problems your HTML editor most likely doesn't handle at all - or handles badly.
And thanks to the design of the HTMLCleanUp main screen shown above, it is very fast to check a large number of files.
A complete check of a 100-page website with only a few errors typically takes a few minutes, incl. correcting the errors on the spot. But you will probably -- like me -- be surprised how many errors you will find the first time you run HTMLCleanUp - and how many you and/or your HTML editor continues to make!