I'm not a developer for this sort of thing, but there is some information not present in the console of my firefox browser. The best I can probably do is just regurgitate it. I have snapshots of my system I can go to and from at least so it's pretty easy to revert.
Before the import:
Use of getAttributeNode() is deprecated. Use getAttribute() instead. load.php5:34
Use of attributes' specified attribute is deprecated. It always returns true. load.php5:34
Use of getPreventDefault() is deprecated. Use defaultPrevented instead. load.php5:48
Use of document.createAttribute() is deprecated. Use element.setAttribute() instead. page-attachment.js:209
Use of setAttributeNode() is deprecated. Use setAttribute() instead.
After the import:
Error in parsing value for 'display'. Declaration dropped. load.php5:1
Unknown property 'zoom'. Declaration dropped. load.php5:1
Expected declaration but found '*'. Skipped to next declaration. load.php5:1
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. load.php5:1
Error in parsing value for 'background-image'. Declaration dropped. load.php5:1
Error in parsing value for 'list-style-type'. Declaration dropped. load.php5:1
Unknown property 'user-select'. Declaration dropped. load.php5:1
Unknown pseudo-class or pseudo-element '-ms-input-placeholder'. Ruleset ignored due to bad selector. load.php5:1
Unknown pseudo-class or pseudo-element '-webkit-search-decoration'. Ruleset ignored due to bad selector. load.php5:1
reflow: 0.11ms function jQuery.support</<, load.php5 line 19
reflow: 0.54ms function jQuery.support</<, load.php5 line 19
reflow: 0.17ms function jQuery.support</<, load.php5 line 19
reflow: 0.12ms function jQuery.support</<, load.php5 line 20
reflow: 0.3ms function jQuery.support</<, load.php5 line 20
reflow: 0.59ms function jQuery.cssHooks[name].get, load.php5 line 109
reflow: 0.24ms
Error: JavaScript parse error: Parse error: Missing ; before statement in file 'MediaWiki:Common.js' on line 5 load.php5:1
reflow: 0.42ms
Error in parsing value for 'unicode-bidi'. Declaration dropped. Main_Page:2
reflow: 0.15ms
reflow: 0.63ms
Use of getAttributeNode() is deprecated. Use getAttribute() instead. load.php5:34
Use of attributes' specified attribute is deprecated. It always returns true. load.php5:34
Unknown property 'user-select'. Declaration dropped. Main_Page:2
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:6
Expected 'none' or URL but found 'alpha('. Error in parsing value for 'filter'. Declaration dropped. Main_Page:6
Use of getPreventDefault() is deprecated. Use defaultPrevented instead. load.php5:48
reflow: 0.15ms
Use of document.createAttribute() is deprecated. Use element.setAttribute() instead. page-attachment.js:209
Use of setAttributeNode() is deprecated. Use setAttribute() instead. page-attachment.js:210
reflow: 2.3ms
reflow: 0.4ms
reflow: 1.15ms
reflow: 0.16ms function jQuery.fn.offset, load.php5 line 141
reflow: 0.39ms
reflow: 0.26ms function <anonymous>, load.php5 line 15
reflow: 0.11ms function <anonymous>, load.php5 line 15
reflow: 0.27ms
Expected 'none' or URL but found 'Alpha('. Error in parsing value for 'filter'. Declaration dropped. Main_Page:2
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:2
Unknown property '-moz-border-radius-topleft'. Declaration dropped. Main_Page:2
Unknown property '-moz-border-radius-topright'. Declaration dropped. Main_Page:2
Unknown property '-moz-border-radius-bottomleft'. Declaration dropped. Main_Page:2
Unknown property '-moz-border-radius-bottomright'. Declaration dropped. Main_Page:2
Unknown property '-moz-border-radius'. Declaration dropped. Main_Page:2
Unknown property 'zoom'. Declaration dropped. Main_Page:8
Expected declaration but found '*'. Skipped to next declaration. Main_Page:8
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:10
Unknown property 'user-select'. Declaration dropped. Main_Page:10
Error in parsing value for 'background-image'. Declaration dropped. Main_Page:10
Expected color but found 'top'. Error in parsing value for 'background-image'. Declaration dropped. Main_Page:10
Expected 'none' or URL but found 'progid'. Error in parsing value for 'filter'. Declaration dropped. Main_Page:10
Error in parsing value for 'background-image'. Declaration dropped. Main_Page:2
Unknown pseudo-class or pseudo-element 'selection'. Ruleset ignored due to bad selector. Main_Page:2
Unknown property 'user-select'. Declaration dropped. Main_Page:2
Unknown property 'column-count'. Declaration dropped. Main_Page:2
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:6
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:2
Error in parsing value for 'white-space'. Declaration dropped. Main_Page:6
Expected 'important' but found 'ie'. Expected ';' or '}' to terminate declaration but found 'ie'. Declaration dropped. Main_Page:4
Unknown property 'user-select'. Declaration dropped. Main_Page:10
Expected 'none' or URL but found 'progid'. Error in parsing value for 'filter'. Declaration dropped. Main_Page:10
Error in parsing value for 'background-image'. Declaration dropped. Main_Page:10
Expected color but found 'top'. Error in parsing value for 'background-image'. Declaration dropped. Main_Page:10
Error in parsing value for 'word-break'. Declaration dropped. Main_Page:10
Unknown property 'overflow-wrap'. Declaration dropped. Main_Page:10
reflow: 0.7ms