It is not always usefull to activate all possible analysis options. A repeated query to the Google Pagerank, for example, is time consuming and wont take an affect or change in rapid succession. Also the content of XML and CSS files does not have to be analyzed in each run. Also image and media files are only subject to limited changes. When disabling certain, for your analysis unnecessary analysis settings, you also increase the entire analysis speed. The analysis settings you will find in the settings dialog under Project -> Analysis.